Juan Martin del Potro will undergo knee surgery for the fourth time but retains hope of playing at the Olympic Games in Tokyo.

Del Potro, who was a career-high world number three in August 2018 and still in the top 10 fewer than two years ago, has not appeared on the ATP Tour since withdrawing from the Queen's Club Championships in 2019.

The 2009 US Open champion had his first procedure after falling at the tournament in London and another followed in January 2020.

The third operation came last August as pain persisted, but the issue still has not been eradicated.

However, Del Potro said in an Instagram post on Monday that the death of his father earlier this year had motivated him to continue pursuing a return to the court.

The 32-year-old, who won bronze for Argentina at the 2012 Olympics and silver four years later, will go under the knife again in Chicago on Tuesday.

"We've tried conservative therapy but the pain is still there," he wrote.

"[Doctor Jorge Chahla] knows I want to play tennis again and be able to play the Olympics, so we agreed that surgery should be done as soon as possible.

"Of course, these last few weeks weren't easy for me. Everything's so hard since my father's passing.

"But also, I feel the strength he sends me from above. I had this day in which I woke up and called the doctor. I knew I had to try again.

"I hope I can overcome this painful situation. I won't stop trying. Of course, your messages and best wishes are always welcomed. Thanks for the love."

German star Alexander Zverev was too strong for top seed Stefanos Tsitsipas in the Mexican Open final, claiming the title in straight sets after a stunning turnaround.

In a battle of the top two seeds, Zverev reigned supreme 6-4 7-6 (7-3) for his 14th ATP crown in Saturday's Acapulco decider.

Last year's US Open finalist Zverev was runner-up at the ATP 500 tournament in 2019, beaten by Australian Nick Kyrgios in straight sets.

But Zverev went one step further this year, taking down two-time Australian Open semi-finalist Tsitsipas after two hours, 17 minutes.

Zverev, who was rocked during his semi-final win over countryman Dominik Koepfer on Friday – a 5.7 magnitude earthquake registered as broadcast cameras shook, did not drop a set throughout his title-winning run.

Greek star Tsitsipas made an impressive start, racing out to a 3-0 lead after breaking Zverev in the second game.

Zverev, though, hit back as he put the set back on serve in the seventh game before consolidating.

Another break saw Tsitsipas come unstuck – Zverev reeling off six consecutive games to claim the opening set in red-hot fashion.

Zverev and Tsitsipas went toe-to-toe in the second set, the pair exchanging breaks late as a tie-break eventually saw the former complete a dominant display.

World number five Stefanos Tsitsipas cruised into the Mexican Open final with a routine victory over Italian teenage sensation Lorenzo Musetti in Acapulco on Friday.

Tsitsipas triumphed 6-1 6-3 in 79 minutes to get past 19-year-old Musetti, who had beaten third seed Diego Schwartzman and former world number three Grigor Dimitrov on his run to the semis.

The Greek top seed will play second seed Alexander Zverev in Saturday's final after the German got past countryman Dominik Koepfer 6-4 7-6 (7-5) in their semi-final, which was literally rocked by an earthquake.

The broadcast cameras shook mid-point but play continued as a 5.7 magnitude earthquake was registered to the north of Marquelia, which is to the east of Acapulco.

Tsitsipas holds a 5-1 record against Zverev, who is ranked seventh in the world and made last year's US Open final.

"Sascha is someone I've played against in the past and it's never easy. We're both really hungry and we're both very competitive," Tsitsipas said.

The Greek made light work of Musetti, winning five straight games in the opening set after starting at 1-1.

Unforced errors cost Musetti, who had his moments, but Tsitsipas was on song with 17 of 23 winners off his forehand.

Musetti will move into the top 100 of the rankings for the first time on Monday after his breakthrough week.

"We'll definitely see a lot from Lorenzo in the future, he has a wonderful one-handed backhand and creates lots of opportunities. He showed his level this week," Tsitsipas said.

An earthquake hit Acapulco during Alexander Zverev's clash against Dominik Koepfer at the Mexican Open on Friday.

The broadcast camera shook mid-point during the all-German semi-final encounter.

A 5.7 magnitude earthquake was registered to the north of Marquelia, which is to the east of Acapulco.

Zverev went on to secure a 6-4 7-6 (7-5) victory over Koepfer to reach the final.

World number one Novak Djokovic has joined Rafael Nadal and Roger Federer in deciding not to play at the Miami Open, which begins next week.

The Masters 1000 tournament has not been its usual big draw for the leading men this year, and Djokovic becomes the latest high-profile withdrawal.

The 33-year-old Serbian announced he would enjoy some family time rather than travel to the United States, citing the need for balance in his life as coronavirus restrictions affect globe-trotting sports stars.

Miami's total prize fund is said to have been cut from $16.7million in 2019, the last time it was held, to $6.68m this year.

That drastic reduction, reported by the Tennis Majors website, may or may not have been a partial factor in the withdrawals that have dented the top-tier quality in the men's side of the tournament.

The women's event looks like being a full-strength field, while new world number two Daniil Medvedev is set to be the men's top seed, providing he makes the trip.

Djokovic wrote on Twitter: "Dear fans, I'm very sorry to announce that this year I won't travel to Miami to compete.

"I decided to use this precious time at home to stay with my family. With all restrictions, I need to find balance in my time on tour and at home. I look forward to coming back next year!"

Nadal has been bothered by a back problem and cited it earlier this week as the reason for his withdrawal, as he looks to recover full fitness in time for the clay-court season and a crack at winning a 14th French Open title.

The Spaniard's great rival Federer, a fellow 20-time grand slam winner, has only just returned from a year away from the tour after knee surgery, and beat Dan Evans in his first match back at the Qatar Open before losing to Nikoloz Basilashvili.

Federer then elected not to play in Dubai and will not be in Miami, where he is the men's reigning champion, having taken the 2019 title. The 2020 tournament was cancelled because of the COVID-19 crisis.

Top seed Stefanos Tsitsipas was made to sweat but got past Felix Auger-Aliassime in three sets to reach the Mexican Open semi-finals on Thursday.

World number five Tsitsipas, who was a semi-finalist at last month's Australian Open, defeated seventh seed Auger-Aliassime 7-5 4-6 6-3 in Acapulco.

In a tight contest, back-to-back double faults from Canadian sensation Auger-Aliassime in the eighth game of the third set proved costly as Tsitsipas broke after the pair had held serve throughout the last.

"It got really tight," Tsitsipas said in his post-game interview. "I got a bit lucky with the double faults towards the end of the match.

"I was just persistent. Towards the end I had zoned in 100 per cent. Both of us brought an amazing energy out on the court. Felix is someone I've played a lot and I have huge respect for him."

Greek star Tsitsipas will next play emerging Italian teenager Lorenzo Musetti for a spot in the ATP 500 tournament decider.

Qualifier Musetti, who upstaged third seed Diego Schwartzman in the first round, stunned fifth seed Grigor Dimitrov 6-4 7-6 (7-3) in the final match of the day.

The 19-year-old Musetti will now contest his maiden ATP 500-level semi-final as he prepares to enter the top 100 on the men's tour after just his fourth main-draw appearance.

Alexander Zverev – the German second seed – progressed to the semi-finals with a walkover after eighth seed Casper Ruud withdrew due to a wrist injury sustained in practice.

Zverev will play countryman Dominik Koepfer in the final four after he defeated Cameron Norrie 7-5 6-4, maintaining his run of not dropping a set all tournament.

Denis Shapovalov secured a straight-sets win over Jeremy Chardy to set up a semi-final showdown with qualifier Lloyd Harris at the Dubai Tennis Championships. 

The third seed struck 26 winners en route to a 7-5 6-4 triumph on Thursday, but it was his serve that pleased him most.

Shapovalov, ranked 12th in the world, sent down 10 aces as Frenchman Chardy was deprived of any break-point openings.

"I've focused on my serve a lot in the past couple of weeks," the Canadian said.

"I have worked on placing it and tried out different types of serves to have more variation. I hope I can continue that.

"I've also worked on my footwork and positioning during rallies. I am feeling the ball well on both sides. If I am moving well, everything goes into place."

Harris was a surprise winner over Kei Nishikori, sealing a 6-1 3-6 6-3 success to dump out the former world number four.

Second seed Andrey Rublev defeated Marton Fucsovics 7-5 6-2 and will now face fellow Russian Aslan Karatsev.

Wildcard Karatsev continued his run with a hard-fought victory over teenager Jannik Sinner, coming from a set down in a 6-7 (5-7) 6-3 6-2 win.

Top seed Stefanos Tsitsipas and fellow star Alexander Zverev progressed to the Mexican Open quarter-finals on Wednesday, but Milos Raonic bowed out.

Tsitsipas was too good for big-serving American John Isner in a 6-3 6-2 victory in Acapulco midweek.

A two-time Australian Open finalist, having also reached the French Open final four last year, Tsitsipas excelled on serve against Isner.

Greek star Tsitsipas only dropped one point on his first serve – not facing a break point throughout the last-16 contest – while firing down eight aces.

Standing in the way of Tsitsipas and a semi-final spot at the ATP 500 tournament is Canadian sensation Felix Auger-Aliassime.

In a battle of the NextGen, seventh seed Auger-Aliassime saved four of five break points in a 6-3 6-4 win over wild card Sebastian Korda.

Zverev will feature in his third Mexican Open quarter-final in four years after the second seed took down Laslo Djere 6-4 6-3.

Runner-up in 2019, Zverev will next face eighth seed Casper Ruud – who topped Tallon Griekspoor 4-6 6-3 7-6 (7-3) in the quarters.

"I think today what showed the most is that I got better with the match," Zverev said. "I started off extremely sloppy, started off with a lot of unforced errors.

"The longer the match went on the better I started playing and this is something that is very important for me. When I get into a rhythm I feel very comfortable on court and that's how I felt today."

Elsewhere, Lorenzo Musetti's giant-slaying run continued following a 2-6 6-3 7-6 (7-1) victory against Frances Tiafoe.

Musetti earned his first ATP 500 quarter-final as the Italian prepares to meet fifth seed Grigor Dimitrov, who eased past Miomir Kecmanovic 6-4 6-2.

There was an upset after fourth seed Raonic crashed out 6-4 6-2 at the hands of Dominik Koepfer, while sixth seed Fabio Fognini lost 6-4 6-3 against Cameron Norrie.

Jannik Sinner fought hard to earn an impressive victory that knocked fourth seed Roberto Bautista Agut out of the Dubai Tennis Championships. 

The 19-year-old rising star, who won the Great Ocean Road Open last month, prevailed in a match that remained in the balance until the end on Wednesday. 

Sinner won 6-4 3-6 7-5 to reach the quarter-finals, with Bautista Agut following top seed Dominic Thiem - who lost in the second round - out of the tournament. 

After hitting 16 aces, Sinner – the youngest player in the ATP Tour top 100 – will face surprise Australian Open semi-finalist Aslan Karatsev next. 

Second seed Andrey Rublev is through after a comfortable 6-3 6-1 win over Taylor Fritz. 

Rublev will face Marton Fucsovics, who ousted Serbian Dusan Lajovic in three sets, in the last eight. 

The Russian now has 22 consecutive wins at ATP 500 events, a run that has included four titles at that level. Only Roger Federer has ever recorded a longer streak, doing so with a run of 28 between 2014 and 2016.

"I am really happy that I can win in straight sets and quite confidently," Rublev said. 

"I know Taylor since [the] juniors and it is always tough to play against him, because he has a huge serve and he is playing really fast. 

"The first set was not even rallies because everything was serve, winner or serve, mistake, so everything was so fast. 

"In these conditions, it is tough to find the rhythm. You don't know what's going to happen and it's really not easy, but I'm happy that in the end I made it."

Third seed Denis Shapovalov is also through after a 6-4 6-3 win over Hubert Hurkacz, the Canadian booking a last-eight meeting with Jeremy Chardy. 

Kei Nishikori will play Lloyd Harris in the other quarter-final. 

Italian qualifier Lorenzo Musetti may be ranked 120th in the world but he claimed his maiden top-10 scalp on Tuesday, beating Diego Schwartzman in the first round of the Mexican Open.

Musetti, the Australian Open boys' singles champion in 2019, secured a 6-3 2-6 6-4 win over ninth-ranked Schwartzman in a stunning success.

"There is a lot of work, a lot of sacrifice and I think some tears left in my eyes," the 19-year-old said during his on-court interview.

"I'm really proud of myself, but now I'm going to work harder and focus on the next days."

Musetti, whose forehand was excellent, defeated both Stan Wawrinka and Kei Nishikori at the Internazionali d'Italia in Rome last year.

Top seed Stefanos Tsitsipas had no such trouble, easing into the second round, where he will face big-serving American John Isner.

The Greek world number five beat France's Benoit Paire 6-3 6-1, aided by a strong display on serve.

"I didn't know what to expect from Benoit today," Tsitsipas said. "I think it's kind of tricky playing a tournament you haven't played before."

On facing 27th-ranked Isner next up, Tsitsipas added: "He's a guy that serves really well so that's going to be the biggest element and the one thing that I'll really have to resolve during that match."

Fourth seed Milos Raonic sent down 13 aces as he defeated American Tommy Paul 7-6 (8-6) 6-4.

In the late match, fifth seed Grigor Dimitrov got past Adrian Mannarino, who retired when trailing 6-4 3-0.

Alexander Zverev cruised into the second round of the Mexican Open as debutant Sebastian Korda enjoyed a memorable debut in Acapulco.

German star and second seed Zverev accounted for teenager Carlos Alcaraz, the 2019 runner-up winning the opening-round clash 6-3 6-1 on Monday.

Alcaraz – in his first showdown against a top-10 player – broke for a 2-0 lead and while he continued to go toe-to-toe with Zverev through six games, the 17-year-old was unable to maintain his charge.

Zverev broke for a 4-3 lead and the 2020 US Open finalist did not look back, winning nine of the last 10 games to advance in 84 minutes.

"He started off playing extremely well, he didn't miss a lot of balls. Then I felt more comfortable on court, this is the first round," Zverev said.

"It's not always easy to play a first round, especially against a player like this, who is very young, who is very motivated and who wants to compete. I'm actually quite happy with how the match went."

Next up for Zverev – who reached the Australian Open quarter-finals in February – is Serbia's Laslo Djere.

Djere took down Steve Johnson 6-2 6-3 for a spot in the last 16.

Meanwhile, Korda capped his Acapulco bow with a shock 7-5 6-2 win against former world number three Marin Cilic.

Korda claimed his first ATP 500-level victory having saved 10 of the 11 break points he faced in the opening set against the 2014 US Open champion.

Canadian sensation and seventh seed Felix Auger-Aliassime awaits after the 20-year-old converted his sixth match point to see off Tennys Sandgren 6-3 7-6 (10-8).

Elsewhere, John Isner and Dominik Koepfer also advanced.

Former world number one Andy Murray will compete at the Miami Open for the first time since 2016 after being granted a wildcard.

Murray has not played on the ATP Tour since last month's Rotterdam Open, where the three-time major champion lost to Andrey Rublev in the round of 16.

But Murray – who won the ATP 1000 event in 2009 and 2013 – is set to end his Miami absence, having undergone hip surgeries in 2018 and 2019.

"It's a city I love, and I've spent a lot of time here over the last 15 years, I feel comfortable," the 33-year-old, who sat out the Australian Open after testing positive for coronavirus, told PEOPLE Magazine.

"But over the next few months, I want to play matches — especially against the top players — work on my game and climb the rankings. I want to get back playing a sport I love."

Murray added: "The last few years has been really hard. After the operation, there were no guarantees I would play again, but I've been working very hard on my conditioning and over the last few months I've felt the best I have for years. 

"I'll need to be mindful of my schedule moving forward but I'm excited to be back competing — with a metal hip."

"But every match feels like progress and I'm learning from each one," he continued.

The Miami Open will get underway at Hard Rock Stadium on March 24 after the tournament was cancelled last year amid the COVID-19 pandemic.

"It is exciting to see Andy back in Miami," Miami Open Tournament Director James Blake said.

"As someone who has had to battle back from injuy during his career, I understand and respect all the hard work Andy has put in to get back on tour."

Cristian Garin prevailed in his hometown, crowned Chile Open champion with a three-set victory over Facundo Bagnis.

Garin, who had not won a match in 2021 before arriving in Santiago, claimed his first ATP Tour trophy on home soil thanks to Sunday's 6-4 6-7 (3-7) 7-5 triumph.

The top seed and 24-year-old only dropped one set throughout the ATP 250 tournament as he became the first Chilean player to win a home event since Fernando Gonzalez in 2009.

Bagnis was contesting his first final aged 31 and he was unable to see it through against Garin, who celebrated his fifth ATP title – all of them on clay.

Daniil Medvedev claimed the 10th ATP Tour title of his career with a 6-4 6-7 (4-7) 6-4 win over Pierre-Hugues Herbert at the Open 13 Provence in Marseille.

Medvedev will move up to number two in the world in Monday's latest ranking, making him the first player outside of the big four of Roger Federer, Rafael Nadal, Novak Djokovic and Andy Murray to occupy one of the top two positions since Leyton Hewitt in 2005.

The Russian celebrated this achievement with a dogged display to down Herbert in two hours and 11 minutes, saving four of the five break points he faced.

A finalist at the Australian Open, Medvedev is now 14-2 in 2021, with the Open 13 title his sixth on indoor hard courts.

Herbert's strategy of frequently visiting the net was initially picked apart by Medvedev, who only needed one set point in the opener as he threaded a backhand winner expertly down the line.

But the Frenchman applied the pressure in set two, passing up three break points early on before impressing from the baseline to reel off five straight points and claim the breaker from 2-4 behind.

The decider was a tense affair but Herbert's errors at the net came back to undermine his efforts decisively when he served to stay in the match at 5-4.

The 29-year-old has now lost all four of his ATP Finals, while Medvedev again proved himself to be a high-quality operator on such occasions.

Top seed and local hope Cristian Garin progressed to Sunday's Chile Open final after defeating Daniel Elahi Galan in straight sets in their semi-final.

The Chilean world number 22 triumphed over Colombian Galan 6-4 6-3 and will play 118th-ranked Facundo Bagnis in Sunday's decider in Santiago.

Garin sent down eight aces and was dominant on his first serve against Galan.

Santiago native Garin, 24, has never won an ATP Tour title on home soil, while no Chilean has won the event since Fernando Gonzalez in 2009.

"I'm so, so happy to be in the final," Garin said in his post-game on-court interview. "The first day that I arrived I wasn't playing well and it was my second tournament in months, so for me to be in the final is so special, and even more here in Chile."

Argentinian Bagnis defeated higher-ranked countryman Federico Delbonis 7-5 6-3 to secure his place in a maiden Tour final.