Serena Williams' long and illustrious tennis career looks to have drawn to a close after the American lost to Ajla Tomljanovic at the US Open on Friday. 

Following a long piece in Vogue last month, Williams wrote of her plan to "move in a different direction" after "these next few weeks", suggesting the tournament at Flushing Meadows would be her last outing.

Thanks to her success and brilliance on the court, Williams has become synonymous with tennis and is regarded by many as the greatest the women's sport has ever seen.

At the age of 40, Williams has persisted with tennis far longer than most do, and that is testament to her quality and enduring desire for success.

Though Williams left a glimmer of a chance that she may yet play again, joking that she "always did love Australia", she may well have taken to the court for the last time. Here, Stats Perform takes a look at the key facts, stats and figures of her career; in other words, Serena's remarkable legacy.

Twenty-three… and done?

Of course, the headline fact for Williams' career is her grand slam titles count.

She has won 23, which is more than anyone else in the Open era.

But she still had one target left: matching Margaret Court. The Australian's 24 grand slam successes include nine won before the Open era began in 1968, though her overall total has been the benchmark ever since she claimed her final crown at the US Open in 1975.

Clearly, victory for Williams at Flushing Meadows would have been the perfect farewell, but it was not to be. Will that near-miss encourage her to take one more shot in Court's homeland next year?

The finals hurdle

Had Williams managed to reach the championship match in Queens, she would have equalled another record.

She headed into the US Open having played in 33 grand slam finals, one more than Martina Navratilova.

But Chris Evert (34) sits out in front, and that record is now set to remain hers for many, many years.

Top of the pile

It's been a while now since Williams was last the highest-ranked player in the world, but in a way that only further highlights how remarkable her career has been.

She's spent 319 weeks ranked as world number one, which is behind only Steffi Graf (377) and Navratilova (332).

While many might have expected Williams to have been top of the pile for even longer, it's worth remembering how she's spent time out due to injuries and pregnancy, with her general involvement in top-level tennis decreasing after 2014 when she played 16 tournaments – in 2016 that halved to eight, and during no year since has she played in more.

Additionally, some will also be surprised to learn she actually only finished the year as the top-ranked female player five times. Nevertheless, that's still third to only Graf (eight) and Navratilova (seven).

Go hard or go home

Such has been Williams' quality, she was always considered a threat regardless of the surface – she's won each grand slam at least three times.

But there's no denying she was at her most lethal on hard courts.

She has won 48 WTA Tour-level titles on hard courts, which is 11 more than anyone else (Graf) in the Open era.

Those 48 come from a grand total of 73 across all surfaces, leaving her ranked fifth behind Navratilova (167), Evert (157), Graf (107) and Court (92).

Surface to say…

Williams' comfort on hard courts goes even further than that.

She's won 541 matches on the surface, making her one of just two female players to surpass 500 victories on one specific ground type.

Navratilova (600 on carpet) is the only other player to achieve the feat, with Serena's sister Venus (498 on hard) the closest to the 23-time grand slam champion.

The grass is greener

Despite that unrivalled excellence, hard courts may not be the surface many feel to be most synonymous with Williams, however.

Wimbledon is the tournament that would appear to be her favourite.

She's reached the final at SW19 11 times. Only Navratilova can better that record for the most finals at one tournament – though it's worth saying she contested the WTA Finals and Chicago 14 times each, Eastbourne 13 times and 12 at Wimbledon.

Serena Williams' long and illustrious tennis career looks to have drawn to a close after the American lost to Ajla Tomljanovic at the US Open on Friday. 

Following a long piece in Vogue last month, Williams wrote of her plan to "move in a different direction" after "these next few weeks", suggesting the tournament at Flushing Meadows would be her last outing.

Thanks to her success and brilliance on the court, Williams has become synonymous with tennis and is regarded by many as the greatest the women's sport has ever seen.

At the age of 40, Williams has persisted with tennis far longer than most do, and that is testament to her quality and enduring desire for success.

Though Williams left a glimmer of a chance that she may yet play again, joking that she "always did love Australia", she may well have taken to the court for the last time. Here, Stats Perform takes a look at the key facts, stats and figures of her career; in other words, Serena's remarkable legacy.

Twenty-three… and done?

Of course, the headline fact for Williams' career is her grand slam titles count.

She has won 23, which is more than anyone else in the Open era.

But she still had one target left: matching Margaret Court. The Australian's 24 grand slam successes include nine won before the Open era began in 1968, though her overall total has been the benchmark ever since she claimed her final crown at the US Open in 1975.

Clearly, victory for Williams at Flushing Meadows would have been the perfect farewell, but it was not to be. Will that near-miss encourage her to take one more shot in Court's homeland next year?

The finals hurdle

Had Williams managed to reach the championship match in Queens, she would have equalled another record.

She headed into the US Open having played in 33 grand slam finals, one more than Martina Navratilova.

But Chris Evert (34) sits out in front, and that record is now set to remain hers for many, many years.

Top of the pile

It's been a while now since Williams was last the highest-ranked player in the world, but in a way that only further highlights how remarkable her career has been.

She's spent 319 weeks ranked as world number one, which is behind only Steffi Graf (377) and Navratilova (332).

While many might have expected Williams to have been top of the pile for even longer, it's worth remembering how she's spent time out due to injuries and pregnancy, with her general involvement in top-level tennis decreasing after 2014 when she played 16 tournaments – in 2016 that halved to eight, and during no year since has she played in more.

Additionally, some will also be surprised to learn she actually only finished the year as the top-ranked female player five times. Nevertheless, that's still third to only Graf (eight) and Navratilova (seven).

Go hard or go home

Such has been Williams' quality, she was always considered a threat regardless of the surface – she's won each grand slam at least three times.

But there's no denying she was at her most lethal on hard courts.

She has won 48 WTA Tour-level titles on hard courts, which is 11 more than anyone else (Graf) in the Open era.

Those 48 come from a grand total of 73 across all surfaces, leaving her ranked fifth behind Navratilova (167), Evert (157), Graf (107) and Court (92).

Surface to say…

Williams' comfort on hard courts goes even further than that.

She's won 541 matches on the surface, making her one of just two female players to surpass 500 victories on one specific ground type.

Navratilova (600 on carpet) is the only other player to achieve the feat, with Serena's sister Venus (498 on hard) the closest to the 23-time grand slam champion.

The grass is greener

Despite that unrivalled excellence, hard courts may not be the surface many feel to be most synonymous with Williams, however.

Wimbledon is the tournament that would appear to be her favourite.

She's reached the final at SW19 11 times. Only Navratilova can better that record for the most finals at one tournament – though it's worth saying she contested the WTA Finals and Chicago 14 times each, Eastbourne 13 times and 12 at Wimbledon.

Serena Williams hinted that she will return to the court at some point in the future after going down in the third round of the US Open against Ajla Tomljanovic on Friday.

Williams, who saved five match points before eventually succumbing in the three-plus hour marathon, gave an emotional on-court interview where she thanked her family, but also highlighted that she felt like she was getting better as the tournament wore on.

When asked conclusively if this was her final US Open, she was non-committal, saying "you never know".

She took the insinuation that she is not finished playing a step further during her sit-down press conference, laying the breadcrumbs for another go around at the Australian Open.

"I don't know [what it would take to play again] – I'm not thinking about that. I always did love Australia, though," she said with a smile.

"But yeah, you know what, I've come a long way since last year at Wimbledon. Just not sure if that was my last moment or not. Making it a different moment I think is much better.

"And it takes a lot of work to get here. Clearly I'm still capable. It takes a lot more than that. 

"I'm ready to, like, be a mom, explore a different version of Serena. Technically in the world I'm still super young, so I want to have a little bit of a life while I'm still walking."

When asked what she thinks her life will be like moving forward, Williams said she is excited to be able to spend more time with her daughter, and that karaoke is on the agenda.

"I'm definitely resting tomorrow, and then probably spending some time with my daughter," she said. "I'm a super hands-on mom. I've been with her almost every single day of her life, minus two days or three days.

"It's been really hard on her, my career. So it will be, you know, nice just to do that and spend some time with her, do things that I never really have done or had an opportunity to do. I have such a bright future ahead of me, I don't know.

"Also, I'm kind of at an advantage because COVID happened. I think everyone shut down for a year, and we kind of got to see what our lives would be like if we weren't playing tennis. 

"Then I got injured last year, so I took off literally a year. So I got to see, again, like, what every day would be like to wake up and not have to go to the gym.

"So I don't know. I think I'm definitely probably going to be karaoke-ing tomorrow."

Touching on how she would like her career to be remembered, Williams said her unique passion and fire is at the forefront.

"I mean, there's so many things to be remembered by," she said. "Like the fight. I'm such a fighter. 

"I feel like I really brought something, and bring something, to tennis. The different looks, the fist pumps, the just crazy intensity. I think that obviously the passion, I think, is a really good word.

"Just continuing through ups and downs. I could go on and on. But I just honestly am so grateful that I had this moment, and that I'm Serena."

Serena Williams was emotional during her post-match interview in the sold-out Arthur Ashe Stadium after her loss to Ajla Tomljanovic in the third round, thanking her family for their decades of support.

Williams ended up going down in a match that lasted three hours and seven minutes, with a 15-minute final game where Williams saved five match points illustrating her fighting spirit down to the last moments.

If this is her final US Open – which she was hesitant to confirm – she will finish with the most main draw wins ever at the tournament with 108, and her 23 grand slam titles are also the most of all-time.

Speaking on the court after Tomljanovic gladly ceded the floor to the legend, Williams turned her attention immediately to her family as she reflected on the journey to this point.

"Thank you, Daddy. I know you're watching," she said as she began to tear up. "Thanks, Mom… I thank everyone that's here, that's been on my side so many years, decades. Oh, my gosh, literally decades.

"But it all started with my parents – they deserve everything. So I'm really grateful for them. These are happy tears, I guess. I don't know.

"And I wouldn't be Serena if there wasn't Venus, so thank you, Venus. She's the only reason that Serena Williams ever existed."

She added: "It's been a fun ride. It's been the most incredible ride and journey I've ever been on, I mean, in my life.

"I'm just so grateful to every single person that's ever said 'go, Serena' in their life. I'm just so grateful."

When asked if this would definitely be her last US Open, Williams was hesitant due to how well she performed, and left the question unanswered.

"I mean, I'm literally playing my way into this and getting better – I should have started sooner this year," she said with a laugh.

"I don't think so, but you never know. I don't know."

Serena Williams' last US Open has come to an end in the third round, going down 7-5 6-7 (4-7) 6-1 against Ajla Tomlanovic on Friday night.

It was a rough start for Williams, getting her serve broken in the first game of the match, but she got it straight back with a break-to-love by utilising her stunning power.

While her power brought her some easy points, it was also her undoing at times, with 16 unforced errors in the first set compared to 10 winners.

After securing another break to go up 5-3, serving for the opening set, Williams could not finish it off, losing the next four games in a row as Tomljanovic found a way to extend points and turn them into grinding rallies.

Not disheartened, Williams came out on fire in the second set, ripping off the first four games, but Tomljanovic again fought back. From 5-2 down, the Australian surged to level things at 5-5 before forcing a tiebreaker.

In the tiebreaker, Williams worked her way to a 5-4 lead, and took two consecutive mini-breaks to send the crowd into raptures and the match to a deciding set.

But where world number two Anett Kontaveit folded in Williams' last match, Tomljanovic did not, responding instantly after having her serve broken in the opening game to take the next five in a row, with a chance to serve things out at 5-1.

The crowd tried to will the living legend back into the contest, saving the first five of Tomljanovic's match points as she refused to go down easily, but she was not able to convert either of her three break point opportunities in a final game that lasted nearly 15 minutes, ultimately going down on the sixth match point.

After a collective groan in the sold-out Arthur Ashe Stadium, the crowd rose to their feet to pay their respect to the greatest women's tennis player of all time in her final outing at the US Open, as she treated the crowd to one more of her famous twirls at the grand slam she has won six times.

Data Slam: Six-time champion Serena leaves behind records that will stand the test of time

Williams finishes her US Open career with the seven more main draw wins than any other player, male or female. Her 108 wins leads Chris Evert (101), Jimmy Connors (98), Martina Navrilova (89) and Roger Federer (89).

She is also one of five players – along with Navrilova, Federer, Rafael Nadal and Novak Djokovic – to spend at least 300 weeks as the world number one, and her 23 career grand slam titles is the most of any player, leading Steffi Graf (22) and Nadal (22).

WINNERS/UNFORCED ERRORS

Williams – 49/51

Tomljanovic – 32/30

ACES/DOUBLE FAULTS

Williams – 11/7

Tomljanovic – 3/9 

BREAK POINTS WON

Williams – 5/13

Tomljanovic – 8/13

Ons Jabeur has now made it to the second week in all four grand slams after her win over Shelby Rogers at the US Open.

Jabeur, the fifth seed at Flushing Meadows, had previously fallen short of making the second week in the season's final grand slam, having reached the third round in three successive years between 2019 and 2021.

But the Tunisian world number five ended that wait with a 4-6 6-4 6-3 defeat of American Rogers.

Jabeur reached the final at Wimbledon this year, her first appearance in a major showpiece match, but lost to Elena Rybakina.

She has made it to the fourth round of the grand slams six times, having managed quarter-final runs at Wimbledon (2021) and the Australian Open (2020).

Another US Open fourth-round debutant awaits Jabeur in the form of Veronika Kudermetova, who despatched Dalma Galfi 6-2 6-0. 

Kudermetova's victory took just 46 minutes, making it the shortest match of the tournament.

Serena and Venus Williams saw hopes of one last US Open glory run together scuppered by a Czech pair who apologised for knocking out the American superstars.

The Williams sisters lost 7-6 (7-5) 6-4 against Lucie Hradecka and Linda Noskova on Arthur Ashe Stadium, with the doubles match given top billing in the New York night session.

Such scheduling had previously been unheard of, but such is the attention being foisted on the sisters that first-round doubles encounter was the match everyone wanted to see, knowing it could well be the last time the siblings play as a team.

Serena has indicated, albeit couched in somewhat vague terms, that this US Open will be her farewell to tennis. Venus, now 42, may follow suit and also retire from the sport.

While 40-year-old Serena remains in the singles, having beaten world number two Anett Kontaveit in round two to set up a Friday night clash with Ajla Tomljanovic, the dream of one more Flushing Meadows doubles title is over.

It was Czech-out time for the duo who have won 14 grand slam doubles titles together, and Hradecka said sorry to the partisan crowd for spoiling the party.

"I'm still in shock that we won, because we were playing for the first time with each other and I think we did a very good job," Hradecka said.

"I'm so sorry for you that we beat them, but we are so happy that we did it."

Hradecka had been planning on playing with Indian Sania Mirza, but an injury for Mirza put paid to that idea, meaning a new partner was required.

Noskova, 17, answered the 37-year-old Hradecka's call, and enjoyed a night to remember.

"Playing against the Williams sisters is a special moment for everybody, anytime," Noskova said.

"I was really lucky I could play with my doubles partner and we could win and pull out a good fight."

It was the Williams' first doubles match at a grand slam since the 2018 French Open, and their first at the US Open since 2014, and although it was a tight contest the younger pair just had the edge.

Neither sister gave an on-court interview or a press conference after the match, with all eyes now turning towards Serena's singles campaign, and the possibility of that extending deep into the second week.

Serena Williams and sister Venus were unable to advance past the first round of the doubles at the US Open, going down 7-6 (7-5) 6-4 against Czech duo Lucie Hradecka and Linda Noskova on Thursday.

It was the Williams' first doubles match at a grand slam since the 2018 French Open, and their first at the US Open since 2014, less than 24 hours after Serena's stunning upset of world number two Anett Kontaveit.

Leading 5-4 in the first set, the sisters had two opportunities to break and secure the first set, but ultimately let them slip, before going down in a competitive tiebreaker.

They were far from outclassed, winning 48 per cent (49-of-102) of the points in the opening set, and 45 per cent (33-of-74) in the second.

After going down 3-0 in the second frame, instead of rolling over, the Williams sisters fought back, pulling it back to 4-4, but that would be their last stand before dropping the next two games and the match.

There was no on-court interview for the Americans, although 17-year-old Noskova called it "a special moment" and said "I was really lucky" for the opportunity to play against her heroes.

Serena will continue her singles campaign in the third round on Saturday night against unseeded Australian Ajla Tomljanovic.

Alize Cornet is through to the third round of the US Open after defeating Katerina Siniakova 6-1 1-6 6-3, making it the first time she has been beyond the second round of every grand slam in a single season.

Cornet, who defeated reigning champion Emma Raducanu in straight sets to begin her campaign, was terrific with her return game early on, winning 54 per cent of the points off Siniakova's serve in the opening set.

Three double faults for Cornet and the inability to win a single point off her second serve led to a quick second frame for Siniakova, but she steadied in the decider, becoming the first Frenchwoman to win her opening two rounds of each grand slam in a season since Caroline Garcia in 2017.

Cornet has now won five of her past six matches and should be considered a threat given her victory over world number one Iga Swiatek at Wimbledon in July.

She will play the winner between Danielle Collins and Cristina Bucsa in her next match.

Iga Swiatek suggested there has been a lack of leadership at the top of tennis in how to deal with Russia's invasion of Ukraine after Victoria Azarenka was shunned by Marta Kostyuk at the US Open on Thursday.

Ukrainian Kostyuk elected not to shake hands with Azarenka following a second-round defeat at Flushing Meadows, instead merely tapping rackets.

That came after Kostyuk criticised the Belarusian for participating in a charity match for Ukraine, before the United States Tennis Association announced she would no longer be involved.

Belarus maintains close ties with Russia and has been under sanction from western nations for supporting Vladimir Putin after the Russian invasion of Ukraine in March.

Both situations led to a frosty atmosphere following the conclusion of the tie, which Azarenka won 6-2 6-3.

Asked if anything could be done to address tensions between players on the tour, world number one Swiatek, who booked her place in the third round with a 6-3 6-2 win over Sloane Stephens, said: "Well, basically I think it's already too late. I mean, it's never too late, you know, but I think the best time for ATP or WTA to do anything was when the war started, and where the tension was pretty big in the locker rooms.

"I think right now it's already pretty messed up, and maybe next time it's gonna be easier for us to handle it if somebody is going to guide us and somebody is going to even arrange some meetings between players and showing that we should be united.

"Even though there are countries who are invading other countries, we are tennis players. It's sad but it's not our fault that it's happening. Yeah, I think it would be much, much easier at the beginning to do that.

"Right now, it's kind of too late to fix that. But I think it's just in between players and their personal relationships how you're going to handle it and how you're going to communicate to each other.

"But from my case, right now it's easy to say that maybe there was lack of leadership, but at that time I didn't know what to do either. But there are smarter people than me, so they should kind of have an idea."

Victory over Stephens means Swiatek has now won 52 matches in 2022. The last players with more WTA-level wins in a single campaign were Ash Barty (57) and Kiki Bertens (55) in 2019.

Serena Williams is dominating the headlines, though, in what is likely to be her last tournament before retirement – a situation Swiatek is more than happy with. 

Asked if she felt like she was flying under the radar, Swiatek said: "Maybe a little bit, yeah, for sure. You can see the difference than on Roland Garros and on Wimbledon when I came back after winning Roland Garros.

"But I would say it doesn't really matter for me. If I'm going to play well and if I'm going to do my work on court, I know I will be fine in terms of everything that's going around.

"But, yeah, Serena totally deserves it and it's pretty obvious for me that she's going to be in the spotlight in this tournament. That's kind of her time right now. I'm just playing and focusing on that, and that's the most important thing for me."

Swiatek will face Lauren Davis in the next round after the American beat Ekaterina Alexandrova 0-6 6-4 7-6 (10-5). 

Victoria Azarenka was not concerned by being shunned by Marta Kostyuk at the US Open, adding that she has tried to contact the Ukrainian throughout the year.

Kostyuk elected not to shake hands with Azarenka following a second-round defeat at Flushing Meadows, instead merely tapping rackets.

That came after Kostyuk criticised the Belarusian for participating in a charity match for Ukraine, before the United States Tennis Association announced she would no longer be involved.

Belarus maintains close ties with Russia and has been under sanction from western nations for supporting Vladimir Putin after the Russian invasion of Ukraine in March.

Both situations led to a frosty atmosphere following the conclusion of the tie, which Azarenka won 6-2 6-3.

"Well, I wasn't surprised. I don't believe that making a big deal out of it is important. I always shake hands with my opponents. I had the same situation with [Dayana] Yastremska in Washington. It is what it is. I just move on. I cannot force anybody to shake my hand. It's their decision," Azarenka said in a press conference.

Asked if she had spoken to Kostyuk, Azarenka added: "I've offered many times through WTA, because I believe that there is a sort of sensitivity. I've been told that that's not a good time.  

"I don't have, or I never had a close relationship with Marta. I obviously knew who she is, but I've never practiced with her. I've never really had conversation with her.

"So in March when everything happened, I reached out to all the players that I personally know and I still have a good relationship with and, you know, I don't feel that forcing myself to speak to somebody who maybe doesn't want to speak to me for different reasons is the right approach. But I offered."

Kostyuk was asked about the decision not to shake hands and explained her reasons, saying she believed it was not "the right thing" in the current climate.

"I just don't think it's the right thing to do in the circumstances I'm in right now," she said.

"We had a great match, don't get me wrong. She's a great competitor, I respect her as an athlete but that has nothing to do with her being a human being."

Victoria Azarenka has played down the significance of being shunned by Marta Kostyuk at the US Open, adding that she has tried to contact the Ukrainian throughout the year.

Kostyuk elected not to shake hands with Azarenka following a second-round defeat at Flushing Meadows, instead merely tapping rackets.

That came after Kostyuk criticised the Belarusian for participating in a charity match for Ukraine, before the United States Tennis Association announced she would no longer be involved.

Belarus maintains close ties with Russia and has been under sanction from western nations for supporting Vladimir Putin after the Russian invasion of Ukraine in March.

Both situations led to a frosty atmosphere following the conclusion of the tie, which Azarenka won 6-2 6-3.

"Well, I wasn't surprised. I don't believe that making a big deal out of it is important. I always shake hands with my opponents. I had the same situation with [Dayana] Yastremska in Washington. It is what it is. I just move on. I cannot force anybody to shake my hand. It's their decision," Azarenka said in a press conference.

Asked if she had spoken to Kostyuk, Azarenka added: "I've offered many times through WTA, because I believe that there is a sort of sensitivity. I've been told that that's not a good time.  

"I don't have, or I never had a close relationship with Marta. I obviously knew who she is, but I've never practiced with her. I've never really had conversation with her.

"So in March when everything happened, I reached out to all the players that I personally know and I still have a good relationship with and, you know, I don't feel that forcing myself to speak to somebody who maybe doesn't want to speak to me for different reasons is the right approach. But I offered."

Kostyuk was asked about the decision not to shake hands and explained her reasons, saying she believed it was not "the right thing" in the current climate.

"I just don't think it's the right thing to do in the circumstances I'm in right now," she said.

"We had a great match, don't get me wrong. She's a great competitor, I respect her as an athlete but that has nothing to do with her being a human being."

Iga Swiatek is through to the third round of the US Open after securing a routine victory against Sloane Stephens at Arthur Ashe Stadium.

Stephens, who won the 2017 US Open, struggled to keep up with Swiatek as the latter showed her quality on Thursday to win 6-3 6-2.

The number one seed set the tone early by breaking her 29-year-old opponent, and though Stephens responded by breaking straight back, she lost her own service again immediately after.

Swiatek almost broke for a third-straight time but Stephens was able to rescue herself from 15-40 down in the fifth game of the match, though it just delayed the inevitable as the Pole sealed the first set after her opponent hit a backhand effort down the line too long.

There was little sign of a momentum shift as Swiatek broke twice more and raced to a 4-0 lead in the second set.

Though Stephens was taking several games to deuce, Swiatek showed her class to edge over the line in most of them and although the American made the score more respectable with two service holds, it was not enough.

Swiatek confirmed a routine victory with a service hold to love, and will now face another American, Laura Davis, in the next round.

Data Slam: Swiatek's impressive 2022 numbers grow and grow

Swiatek has now won 52 matches in 2022. The last players with more WTA-level wins in a single campaign were Ash Barty (57) and Kiki Bertens (55) in 2019.

The way she is playing at Flushing Meadows, it would not be a surprise to see her overtake Bertens before the end of the tournament.

WINNERS/UNFORCED ERRORS
Swiatek – 14/17
Stephens – 7/18

ACES/DOUBLE FAULTS
Swiatek – 1/2
Stephens – 1/3

BREAK POINTS WON
Swiatek – 4/12
Stephens – 1/2

Serena Williams says this is the most free she has felt on a tennis court in over 20 years after shocking world number two Anett Kontaveit 7-6 (7-4) 2-6 6-2 to advance to the third round of the US Open.

Williams, 40, found another gear in the deciding set as she rode the wave of momentum that came from the raucous, sold-out Arthur Ashe Stadium crowd.

While Williams rose to the occasion, Kontaveit folded, posting three winners and 11 unforced errors in the third set, allowing the all-time great to secure the victory with a break-to-love.

On the court after the match – after a recorded video message from Oprah Winfrey also aired after Monday's win over Danka Kovinic – Williams said while everyone else may have been surprised by the result, she still has supreme confidence in her abilities.

"Well, I'm a pretty good player," she said playfully. "You know, this is what I do best. 

"I love a challenge. I love rising to the challenge. Yeah, I haven't played many matches, but I've been practicing really well. 

"In my last few matches, it just wasn't coming together. I'm like, this isn't me. The last couple matches here in New York, it's really come together."

Williams admitted that she thought to herself "this could be it" after dropping the second set, but highlighted the fact that this is the first time in over 20 years that she does not feel like she has a target on her back.

"Honestly, I'm just looking at [this run] as a bonus," she said. "I don't have anything to prove. I don't have anything to win. I have absolutely nothing to lose.

"Honestly, I never get to play like this since '98 really. Literally, I've had an 'X' on my back since '99. It's kind of fun.

"I really enjoy just coming out and enjoying it. It's been a long time since I've been able to do that."

Lastly, Williams talked about what it will be like to step back out onto the doubles court with sister Venus Williams on Friday night.

"I'm so excited for doubles," she said. "It's like, it's been so long. We got to play again, we got to bring the reunion back.

"I'm excited to play with Venus, get some more practice – because I could use the matches."

The hype around Serena Williams' potential swansong tournament is "the biggest thing I've ever seen in women's tennis", says Torben Beltz, the coach of her next opponent Anett Kontaveit.

Williams has announced she is soon to retire, and the US Open is widely expected to be her final tournament.

The 23-time grand slam champion came through in straight sets in her first-round match against Danka Kovinic to set up a tough meeting with world number two Kontaveit on Wednesday.

Beltz wanted to watch Williams' opening match but could not do so after Arthur Ashe Stadium sold out, with reports of tickets on the secondary market on sale for around $1,000.

And Beltz says he has not seen anything like it, telling the New York Times: "I couldn't get a ticket. 

"This is the biggest thing I've ever seen in women's tennis. I think it's the greatest thing for the sport, and we all have to thank Serena for all she did. Especially right now with the end coming."

While Beltz's charge Kontaveit is favourite for the second-round match, the Estonian's coach knows it will be a tough match against the six-time US Open champion.

"I think her ball speed, serve and return is really up to her prime time," Beltz added.

"I saw her other matches, and it looks like she's improved over the last couple of weeks. She looks in better shape and looks good now.

"For Anett, I think the key is to just go out and try to play her best tennis but also enjoy the moment. It's going to be a big challenge, a great challenge, but I think she wants that challenge and wants to embrace it."