Maria Sakkari sealed victory for top-seeded Greece over Bulgaria in the United Cup with a straight sets win over Viktoriya Tomova.

Team-mates Stefanos Tsitsipas and Despina Papamichail had already won their matches on Thursday, and Sakkari's 6-3 6-2 triumph gave Greece an unassailable 3-0 lead.

Michail Pervolarakis was defeated by Dimitar Kuzmanov in the final singles match between the nations, but Tsitsipas and Sakkari teamed up to earn Greece a 6-4 6-4 success in the doubles encounter to end on a high.

World number 16 Matteo Berrettini helped Italy topple Brazil by overcoming Thiago Monteiro 6-4 7-6 (9-7).

That gave Italy a 2-1 lead, and Lucia Bronzetti finished the job by demolishing Laura Pigossi in straight sets, with Brazil powerless to overturn the deficit despite Berrettini and Camilla Rosatello's defeat in the doubles match.

US Open semi-finalist Frances Tiafoe clinched a win for the United States over the Czech Republic after opponent Tomas Machac retired with an ankle injury with the score at 6-3 2-4.

Petra Kvitova had defeated Jessica Pegula 7-6 (8-6) 6-4 in the third singles match to give Czech Republic hope, but Tiafoe's win settled the contest before Pegula and Taylor Fritz joined up for success in the doubles.

Great Britain were 3-2 victors over Australia despite a pair of defeats on day two in Sydney.

Cameron Norrie's triumph over Nick Kyrgios' replacement Alex De Minaur on day one had helped Great Britain to a 2-0 lead over the hosts, and Harriet Dart prevailed over Maddison Inglis to wrap up the victory.

Dan Evans was then beaten 6-3 7-6 (7-3) by Jason Kubler before Dart and Jonny O'Mara fell to defeat in the doubles, but Great Britain's strong start saw them through.

France and Switzerland completed 5-0 sweeps of Argentina and Kazakhstan respectively, with Caroline Garcia winning both her singles and doubles matches in straight sets while Stan Wawrinka saw off Alexander Bublik 6-3 7-6 (7-3).

Nick Kyrgios accused Australia co-captain Lleyton Hewitt of throwing him "under the bus" following his decision to withdraw from the United Cup.

The 2022 Wimbledon finalist, who has been struggling with an ankle injury, was due to line up alongside the likes of Alex De Minaur and Jason Kubler in the inaugural edition of the team event.

However, Kyrgios surprised team-mates with his decision to pull out of the event, with the 27-year-old switching his focus to achieving full fitness for next month's Australian Open.

Hewitt was unaware of Kyrgios' withdrawal until his public announcement and said he needs to improve his communication skills.  

Kyrgios' withdrawal was followed by that of Ajla Tomljanovic, who pulled out of her match against Great Britain's Harriet Dart due to a knee injury.

Kyrgios responded to a Twitter post about the news, questioning whether co-captain Sam Stosur would respond the same way Hewitt did.

"Mmm I wonder if Stosur will throw her under the bus like our captain did for me... 'hard to prepare when you don't know what's going on'," Kyrgios wrote.

Australia suffered a 3-2 defeat to Great Britain in their Group D meeting, although they will have another chance to progress to the knockout stage when they face Spain next week.

Stefanos Tsitsipas opened his United Cup campaign with a comeback victory over Grigor Dimitrov in Perth.

ATP world number four Tsitsipas is one of the headline names in action at the event, which is acting as a warm-up tournament for the Australian Open.

After going a set down to his Bulgarian opponent in his first game of the inaugural tournament, Tsitsipas hit back with a strong second set before holding his nerve in a tense tie-break in the decider, securing a 4-6 6-2 7-6 (7-4) win.

Tsitsipas's team-mate Despina Papamichail continued Greece's strong start, also coming from a set down to beat Isabella Shinikova 3-6 6-4 6-1.

Great Britain opened with a pair of victories, Cameron Norrie and Katie Swan earning straight sets triumphs over their Australian counterparts in Sydney.

Norrie, who was initially set to play Nick Kyrgios prior to the Wimbledon finalist's withdrawal due to an ankle injury, eased to a 6-3 6-3 victory over Alex De Minaur, while Swan defeated Zoe Hives. 

The United States are also taking a 100 per cent record into day two of the tournament, after Taylor Fritz and Madison Keys overcame Jiri Lehecka and Marie Bouzkova respectively, while France pair Arthur Rinderknech and Alize Cornet got off to winning starts against Argentina's Francisco Cerundolo and Maria Lourdes Carle.

In Brisbane, Swiss hope Belinda Bencic secured a 7-6 (7-0) triumph over Yulia Putintseva of Kazakhstan and Beatriz Haddad Maia, the Brazilian world number 15, dispatched Italy's Martina Trevisan 6-2 6-0.

Novak Djokovic is hoping for a positive crowd reception at the upcoming Australian Open after his deportation prior to the 2022 tournament.

Djokovic is a nine-time Australian Open winner and will be looking to etch his name on the trophy once again in the first grand slam of 2023.

The Serbian was banned from playing at the most recent edition after he was deported due to his refusal to be vaccinated against COVID-19, despite being initially granted a medical exemption.

As a result, Djokovic missed out on the opportunity to lift a record-extending 10th title, as long-time rival Rafael Nadal won the tournament in his absence.

There had been concerns over Djokovic's ability to play in Melbourne this time around, but a change in border entry rules means travellers are no longer required to provide evidence of their vaccination status.

The incident earlier in 2022 did not go down well with some sections of the Australian public, but Djokovic is hoping to receive a warm reception when he takes to the court in Adelaide and then Melbourne.

"I'm hoping everything is going to be positive," Djokovic said at a press conference. "Obviously it's not something I can predict.

"I'll do my best to play good tennis and bring good feelings and emotions to the crowd. This is what we do as professional athletes, we are also entertainers in a way. We try to make people feel good, have fun and go home and have good memories.

"Hopefully that's going to happen with me. I don't know how many matches I'll play but I'm hoping I can go all the way."

As well as the Australian Open, Djokovic's vaccination status also prevented him from competing at Flushing Meadows, and the memories of how he was treated still linger in Djokovic's mind.

The world number five explained: "Obviously what happened 12 months ago was not easy for me, for my family, team, anybody who is close to me. It's obviously disappointing to leave the country like that.

"You can't forget those events. It's one of these things that stays with you for I guess the rest of your life.

"It's something that I've never experienced before and hopefully never again. But it is a valuable life experience for me and something that as I said will stay there but I have to move on. Coming back to Australia speaks [to] how I feel about this country, how I feel about playing here."

Djokovic is drawing on his impressive record in Australia, as he prepares for the grand slam by taking part in the Adelaide International.

"It's great to be back in Australia," he added.

"It's a country where I've had tremendous success in my career, particularly in Melbourne. It's by far my most successful grand slam.

"The good memories and history I have on Australian soil gives me a lot of positive emotions and belief I can do it again and go far.

"I always have faith in myself and belief I can win every tournament I play in, with the career I've had I deserve to have that kind of mental approach."

Djokovic also confirmed he had split from physio Uli Badio after over five years of working together.

The 35-year-old will instead be using the services of Claudio Zimaglia, who most recently worked with Brandon Nakashima.

Novak Djokovic's imminent return to the Australian Open will be good for tennis, according fellow great Rafael Nadal.

Djokovic arrived in Australia this week and will compete in the first of two Adelaide International tournaments before the opening grand slam of 2023 begins on January 16.

In January this year, the 21-time grand slam winner was deported from Australia after being prevented from participating at the last edition of the event, having initially been granted a medical exemption to enter the country despite not being vaccinated against COVID-19.

There were concerns Djokovic would then be banned from entering Australia again, but a change in border entry rules means travellers are no longer obliged to provide evidence of their vaccination status.

While Djokovic's presence may represent a blow to Nadal's hopes of defending the title he clinched in the Serbian's absence last year, the Spaniard is pleased to see him taking part.

"Novak is here, it's good for tennis, probably good for the fans," Nadal said. "Let's see. [Having the] best players on court is always better."

Meanwhile, 22-time grand slam champion Nadal saw his former long-time rival Roger Federer retire this year, but he is not looking to follow suit despite being plagued by injuries in recent months.

Asked whether his upcoming appearance at the Australian Open could be his last, the 36-year-old said: "As a professional, you never know. Hopefully not.

"I mean, when you are at the age of 36, you never know when it's going to be the last one. It's obvious, but I don't like to talk about that because I am not in that mood now.

"I'm just focused on trying to play at the highest level possible and giving myself a possibility to keep being competitive, to fight for anything.

"That's my goal now, I'm not thinking about it being my last time here. If that's the last time, let's try to enjoy it as much as possible and try to create something special.

"I am happy doing what I am doing. I'm looking forward to still doing this."

Nick Kyrgios has withdrawn from the United Cup on the eve of the inaugural edition of the tournament, with Australia team captain Samantha Stosur admitting "it's news to all of us."

The 2022 Wimbledon finalist, who has been struggling with an ankle injury, was due to line up alongside the likes of Alex De Minaur and Ajla Tomljanovic in the new team event.

However, Kyrgios surprised team-mates with his decision to pull out of the event, in which Australia face Great Britain in their opening match on Thursday, reportedly switching his focus to achieving full fitness for next month's Australian Open.

"I'm not going to speak for Nick’s summer, we've got to leave that for him," Stosur said at a press conference. "He was here. We literally just found out 10 minutes ago, so it's obviously news to all of us.

"But we just move forward now. We're all happy to be here and keen to get out there. Now that's out there, and we move forward with the placings of the team and do our best on the day.

"As far as the men's side of this team goes, we're in very capable hands still, so I'm not concerned that our chances have just diminished greatly or anything like that. We're out here to do everything we can possible to try and win this competition."

De Minaur added: "We've all just heard. Ultimately, we're just going to get ready. We’ve got a great team, and we're all going to be out there doing our best. So ultimately, the only thing that changes is match-ups and that's about it."

Rafael Nadal is aiming to "recover positive feelings" ahead of launching his 2023 season at the inaugural United Cup.

The Spaniard became the most successful male player in grand slam history last season as he took his title tally to 22 after landing the Australian Open and French Open.

Only Novak Djokovic and Carlos Alcaraz (both five) won more events on the ATP Tour than Nadal (four) in 2022, but his campaign ended with early exits at the Paris Masters and the ATP Finals.

The 36-year-old will return to action this week at the United Cup, where he lines up alongside the likes of Paula Badosa and Pablo Carreno Busta for Spain, before defending his Australian Open crown.

"The beginning of the season is always exciting," said Nadal, who plays Great Britain's Cam Norrie on Saturday.

"Even if I don't know how many seasons I have on the tour, the start of each year is always different.

"I have the highest motivation to try to start well. It's always important to start well for me, for the confidence.

"The past few months haven't been easy for me. I just try to have the right practice here before the tournament starts. Then of course, try to help the team.

"[The main thing for me now is to recover the positive feelings on court, being competitive. I hope to.

"I am ready to make that happen, but let's see. Only thing that I am focused now is to try to put myself in a competitive level."

Novak Djokovic wants to play for as long as his body is able as he aims to emulate Rafael Nadal and Roger Federer after coming through a challenging 2022 campaign.

Djokovic began last season in somewhat controversial circumstances after he was barred from the Australian Open for his stance on vaccination for the global coronavirus pandemic.

The 21-time grand slam champion lost his world number one spot after failing to defend his French Open crown but roared back to glory at Wimbledon.

A record-matching fifth ATP Finals title took him level with the recently retired Federer and 35-year-old Djokovic has no intentions of slowing down in the new year.

"I would like to play as long as I possibly can," he stated in Dubai on Friday. "I don't have really any number in my head.

"Things are progressing so far pretty well for me. I can't complain. So as long as I play at this level, as long as I have the fire, I'll keep going."

Djokovic may have been unceremoniously deported from Australia earlier this year amid the fallout over his vaccination status but he has enjoyed playing at the first grand slam of the year in recent seasons.

At no other grand slam event has the Serbian been more prolific, with nine titles to date, and he is relishing the chance to start his season in Melbourne once more.

"I'm just glad to have a chance to start there," he added. "My record has been pretty decent over the years in Australia. So I look forward to going there.

"I always ask for the best for myself. Over the years, I've been really fortunate to start very strong in Australia and love playing there.

"After obviously what happened earlier this year, hopefully, I can have a decent reception there, and that can help me play some good tennis."

Rafael Nadal has revealed he had tears in his eyes as Lionel Messi led Argentina to World Cup final glory.

Even for Real Madrid fan Nadal, there was a joy in seeing former Barcelona talisman Messi achieve his greatest feat at an age when some doubted he would ever lift the trophy.

Now 35, Messi was the driving force behind Argentina's success in Qatar. He scored two goals as Sunday's final against France ended in a pulsating 3-3 draw, plus a penalty in the shoot-out that followed, clinching the Golden Ball as the tournament's outstanding player.

For Nadal, who won his 22nd grand slam two days after turning 36 in June, seeing another person achieving late-career success is something to which he can relate.

"Messi lifting the World Cup made me happy. That someone so great culminates with a title that was missing, of this calibre, with all that it means for Argentina, it seemed fair to me," Nadal said.

"I enjoyed it and I was moved. Without siding with Argentina, when Messi scored the third goal tears came to my eyes.

"It was because of the emotion of seeing someone so great achieve what was missing, having suffered so much to achieve it."

Nadal would also have taken a close interest in Kylian Mbappe hitting a hat-trick for France in the Lusail Stadium final, given the Paris Saint-Germain striker is a long-time Madrid target.

Mbappe snubbed Madrid to sign a new PSG contract in May, but it would be no surprise if eventually he ends up at the Santiago Bernabeu.

The matter of Mbappe came up in an interview with AS, who made Nadal their athlete of the year.

Nadal was asked if he would forgive Mbappe if he signed for Madrid.

"I don't have to forgive Mbappe for anything and as a Madrid fan, if he could, come tomorrow," Nadal said.

"In the end, things happen in sports and I suppose that such a young boy was overwhelmed by such tremendous pressure from all angles that in the end... I think he wanted to come to Madrid, but due to many factors, everything was very complicated for him. Hopefully we can see him in Madrid in the future."

Nadal said he would be leaving for Australia on December 26 and cautioned against expecting too much immediately at the start of the new tennis season, pointing to "very difficult" singles matches at the United Cup against Cameron Norrie and Nick Kyrgios.

The Australian Open, where Nadal is the defending men's singles champion, begins on January 16 in Melbourne, with all the focus on getting into prime shape by then.

"Let's see now how the year begins. I'm aware that I'm a little tight here, but I'm confident that I can get to the level I need to be competitive in Australia," Nadal said.

"We'll see what happens. Things change very quickly in sports. But I have the illusion of having a good year again and giving myself options to compete again at the highest level. I am aware that I am the age that I am, and that things happen. I will have to manage it in the best possible way and try to do my best to give myself real options."

Nick Kyrgios has doubled down on the claim he will retire if he wins a grand slam next year, saying years of intensive travel have left him "exhausted".

Kyrgios enjoyed the best grand slam run of his career when he finished as runner-up to Novak Djokovic at Wimbledon this year, while he also reached the last eight at the US Open.

However, the Australian questioned his future in the sport earlier this week, telling reporters in Dubai: "Hopefully I can win a slam and just retire."

Speaking to Eurosport, the world number 22 insisted that remark was serious, saying his private life had suffered due to his time spent travelling to take part in ATP Tour events. 

Asked if he would really call time on his career in the event of winning a first major singles title, Kyrgios said: "Honestly, I probably would.

"Especially being from Australia as well, there's just so much travel, so much time away from family, so much time away from friends. 

"You're just missing milestones in the family, you're just not having a normal life, really. No other tennis player that's not from Australia gets that."

Kyrgios believes few athletes can match the sacrifices he has made in his career, citing the strain caused by spending long periods away from his home country. 

"It's easy for a European or an American player to lose or win a tournament, then you take a five-hour flight back home and you spend a week there before the next event," Kyrgios said.

"Whereas as an Australian, you're doing four- to seven-month travel blocks. Honestly, I don't think it's healthy. 

"No other real athlete does that in the world, in any sport, doing seven months on your own. 

"I'm exhausted honestly. It's just stressful. The more you win, the more success you have, the more demands you have off the court. People expect more from you. 

"People are like, 'why are you complaining about it?' It's not what they think. You're living out of a suitcase at hotels, it's not like you're on holiday. 

"You've got to go to tennis courts and train. The lifestyle is quite vigorous. If it happens, I probably would [retire], to be honest."

Kyrgios has only reached the last eight at the Australian Open on one occasion, and with the next edition of his home slam approaching, the 27-year-old is less than enthusiastic.

Asked if he will feel refreshed by the time the Melbourne major begins next month, Kyrgios said: "Probably not. There is a little bit of excitement, but it's probably 95 per cent stress, five per cent excitement, to be honest."

Andy Murray has conceded he is just one major injury from being forced to retire, though the three-time grand slam winner remains keen to play on.

Murray underwent two hip surgeries in 2018 and 2019, causing him to spend much of the last four years on the sidelines.

However, Murray returned to the top 50 of the world rankings after making two tour-level finals in 2022, while his run to the third round of the US Open represented his joint-best grand slam campaign since Wimbledon 2017.

The two-time Wimbledon champion saw rival Roger Federer retire from the sport in September after struggling with a knee injury, and while he acknowledges fitness concerns could force his hand, Murray is not yet looking to follow suit.

"If my body is in good shape and I'm still able to compete consistently, I'll keep playing," Murray said.

"But I can't look so far in advance with the age I'm at and with the issues I've had. If I was to have a big injury, I probably wouldn't try to come back from that."

Murray has been training with coach Ivan Lendl in a bid to ensure he enters next month's Australian Open in peak condition, having missed three of the last five editions of the tournament.

"I spent three weeks in Florida, getting my body right and getting some work done on my game and it went really well," he said.

"I'm certainly in better shape than I was. A lot of work was done in the gym, trying to build up my endurance and my stamina a bit and I'm hoping that's going to help me next year.

"I wasn't happy with how last season went – certainly the last six months or so from a physical perspective – but my ranking still went from 125 to 50 in a year. 

"I'm hoping that this year, with the work I've done, things will continue to improve and I'll still be motivated to get out there and compete."

Boris Becker described his time in prison as “the loneliest moment I've ever had” but "I believe I rediscovered the human in me" after he was released last Thursday.

Six-time grand slam singles champion Becker was sentenced to two and a half years in jail in April after being found guilty of hiding £2.5million worth of assets and loans to avoid paying debts when he was declared bankrupt in 2017.

The German reportedly spent the first few weeks of his sentence at Wandsworth Prison in London before being moved to the low-security Huntercombe prison in Oxfordshire in May.

The 55-year-old served just eight months of his sentence before being allowed out and has returned to his homeland, with reports he is not allowed back in the United Kingdom for a decade.

In an interview with Sat.1 that was broadcast on Tuesday, the tennis legend has opened up on the dark days he has experienced but says he has learned a "very expensive" lesson.

"In prison you are a nobody, you are only a number. Mine was A2923EV," he recalled when breaking his silence. "I wasn't called Boris, I was a number. And nobody gives a s*** who you are.

"When the cell door closes, the whole world collapses. This is the loneliest moment I've ever had. 

"There is only you with your thoughts. There's a carousel in your head, of course. You try to breathe calmly. I was afraid, I didn't cry.

"I believe I rediscovered the human in me, the person I once was. I've learned a hard lesson. A very expensive one. A very painful one. 

"But the whole thing has taught me something very important and worthwhile. And some things happen for a good reason."

Recalling the day of his release, Becker, who lived in London before he was sent to prison, said: "From six o'clock that morning I sat on the edge of my bed, and hoped that the cell door would open. 

"They came to get me at 7.30am, unlocked the door and asked: 'Are you ready?' I said: 'Let’s go!' I had already packed everything beforehand."

Nick Kyrgios could "just retire" if he wins a grand slam in the upcoming 2023 season.

The Australian had one of his best years yet in 2022, winning three doubles titles and also collecting the Washington Open singles final in August.

However, Kyrgios fell short again at the season's grand slams despite reaching the Wimbledon final, where he was defeated by Novak Djokovic in four sets.

With the Australian Open, Kyrgios' home tournament and first grand slam of the year, less than a month away, the 27-year-old could call it quits should he win a maiden grand slam.

Speaking between matches at an exhibition event, Kyrgios told reporters: "Hopefully I can win a Slam and just retire.

"Would I sign again? Honestly, I don't know about it.

"It took a lot of hard work this [2022] season, a lot of discipline and it seems the better you do, everyone wants a bit more of you and it becomes more stressful.

"But I had a lot of fun this season. And I’m finally just proud to say I made a Slam final and started to meet some expectations. I had a lot of fun, I enjoyed it, definitely felt better off and on the court."

It is not the first time Kyrgios has suggested an early retirement, having stated in October he will "probably not" play past the age of 30.

Rafael Nadal has made a swift appointment after long-time ally Francis Roig left his coaching team.

The record 22-time men's grand slam singles champion has brought in Argentinian Gustavo Marcaccio to work with lead coach Carlos Moya and Marc Lopez.

Nadal announced on Friday that Roig was departing, having worked with the Spaniard since 2005, to take on "a new project".

With the new ATP season just days away from beginning, Marcaccio has accepted the chance to step in, with the 45-year-old having held a position at Nadal's academy in Mallorca for the past 20 months.

Marcaccio had a mostly undistinguished playing career, reaching a high of 284th on the rankings, but he has strong coaching credentials, having worked with the likes of Juan Monaco, Svetlana Kuznetsova and Guido Pella.

Nadal wrote on Twitter: "Hello everyone. I want to inform you of the incorporation of Gustavo Marcaccio to the technical team.

"Gustavo has been working at the @rafanadalacademy since April 2021 and I understand that he is a good addition to the team. I am sure he will help us a lot to follow the path. Welcome!"

Nadal will return to Melbourne as the defending champion at the Australian Open in January, having won that and the French Open in 2022 to move ahead of Roger Federer and Novak Djokovic on the men's all-time grand slam list.

Cameron Norrie is hoping Russian players will be allowed to return to Wimbledon in 2023, saying he wants "the best players in the world to be playing".

Following the Russian invasion of Ukraine earlier this year, Russian players were banned from participating at SW19.

This meant the likes of Daniil Medvedev and Andrey Rublev were not able to play and compete for the third grand slam of the year, which Novak Djokovic ended up winning for the seventh time.

The tournament was stripped of ranking points as a result of the ban on Russians, a decision that was met with much frustration from players.

Medvedev and Rublev finished a respective seventh and eighth in the year-end ATP rankings, and both took part in the ATP Finals in Turin.

Norrie hopes they are able to return to Wimbledon next year, telling reporters: "For me, I want the best players in the world to be playing.

"I felt last year was tough for those guys, especially for Daniil and for Andrey, who have a chance of winning Wimbledon.

"I know how much those guys sacrificed with their careers and their goals are obviously very high to be winning Slams.

"So I really did feel bad for those guys."