Iga Swiatek dragged Poland into the semi-finals of the United Cup with inspired performances in her singles and doubles matches against Italy.

Poland trailed after Lorenzo Musetti and Matteo Berrettini secured wins against Daniel Michalski and Hubert Hurkacz respectively, only for Swiatek and Magda Linette to level things with respective singles victories over Martina Trevisan and Lucia Bronzetti.

That sent the Brisbane city final to a decider in the mixed doubles, which Swiatek and Hurkacz won with ease 6-1 6-2 against Musetti and Camilla Rosatello, though there was a pause in the second set to dry rainfall on the court.

Despite defeat, Italy also advanced to the final four as the city finals loser with the best record.

It was more routine in Sydney as the United States eased to a 4-1 win against Great Britain.

Madison Keys came from a set down to beat Katie Swan, while Jessica Pegula eased past Harriet Dart 6-2 6-0 after Cameron Norrie had defeated Taylor Fritz in three sets.

Despite going a set behind, Frances Tiafoe came back to beat Dan Evans 3-6 7-5 6-3 to clinch the win for his country, before Pegula and Fritz added some gloss after beating Dart and Evans in the mixed doubles.

The third city final in Perth included a thriller as Greece's Stefanos Tsitsipas beat Borna Coric 6-0 6-7 (4-7) 7-5. Donna Vekic had no trouble getting Croatia on the board as she eased past Despina Papamichail 6-2 6-0.

Maria Sakkari put Greece 2-1 ahead when she beat Petra Martic 6-3 6-3, but Borna Gojo defeated Stefanos Sakellaridis in straight sets to make it 2-2.

However, Greece secured the win and their place in the last four after the pairing of Sakkari and Tsitsipas saw off Martic and Gojo 7-6 (8-6) 6-4.

Greece will take on Italy in the semi-finals, while Poland face the USA, with both taking place in Sydney on Friday.

Daniil Medvedev cruised into the quarter-finals of the Adelaide International with a straight-sets victory over Miomir Kecmanovic on Wednesday.

The Russian, seeded third in South Australia, made short work of his Serbian opponent in a 6-0 6-3 win to reach the last eight with little hassle.

"It's always better to win 6-0 than to win 7-6 saving nine set points and playing one hour, 20 [minutes]," Medvedev said.

"But tennis is not as easy, otherwise everyone would be number one, but we have only one. So happy with my level today against a strong opponent. Second set was tougher, but managed to close it out at the end and looking forward to my next matches."

It sets up a match with countryman Karen Khachanov, who defeated Britain's Jack Draper in a 6-4 6-2 straight sets victory of his own at Memorial Drive Tennis Centre.

Japan's Yoshihito Nishioka will also compete in the quarter-finals after a 6-4 6-3 win over American Mackenzie McDonald, and will face home favourite Alexei Popyrin.

At the Tata Open Maharashtra in Pune, top seed Marin Cilic needed to survive a second-set fightback from Spain's Roberto Carballes Baena before he progressed 6-3 3-6 6-1.

Aslan Karatsev meanwhile took a two-set thriller against Tim van Rijthoven, prevailing in a 7-6 (9-7) 7-6 (10-8) triumph.

Novak Djokovic is set to miss the Indian Wells Open and Miami Open after the United States extended the requirement for all non-American nationals to be vaccinated against COVID-19.

The 21-time grand slam winner was forced to sit out both tournaments last year, as well as other events in America and Canada, due to not being vaccinated.

Whereas many countries are relaxing vaccination requirements, meaning Djokovic is able to compete in this year's Australian Open, US travel authorities are asking for proof of being fully vaccinated against coronavirus to enter the country until at least April 10.

That will see Djokovic sit out the prestigious Indian Wells between March 6 and March 19, and the Miami Open between March 20 and April 2.

Djokovic is currently competing in the Adelaide International, where he kicked off his season with a 6-3 6-2 win over Constant Lestienne on Tuesday, ahead of beginning his quest for a 10th Australian Open crown later this month.

The Serbian was deported from Australia this time last year after his visa was revoked due to his unvaccinated status and was initially banned from entering the country for three years, but that was waived in November.

Wins for Hubert Hurkacz and Magda Linette saw Poland advance to the City Finals of the United Cup in Australia on Tuesday.

Hurkacz made it through a tough encounter against Stan Wawrinka 7-6 (7-5) 6-4 to give Poland a 2-1 lead in their Group B tie with Switzerland in Brisbane, before Linette came from behind to beat Jil Teichmann 5-7 6-4 6-1 to clinch it.

Poland will face Italy in the Brisbane final, whose 5-0 whitewash of Norway included Matteo Berrettini sealing victory with a 6-4 6-4 win over Casper Ruud.

In Perth, Croatia advanced to the City Finals after a dramatic day that saw Caroline Garcia get France on the board with a straight sets win against Petra Martic, before Adrian Mannarino came from a set down against Borna Gojo to serve for the match as he looked to bring his country level at 2-2.

However, Gojo broke back in a tense encounter before winning a deciding tie-break to send Croatia through to face Greece, who sealed a 4-1 win against Belgium.

Stefanos Sakellaridis recovered from going a set behind to beat Zizou Bergs, before Maria Sakkari overcame Elise Mertens 6-1 7-5, with Sakkari and Stefanos Tsitsipas adding some gloss to the score with a mixed doubles success against Kirsten Flipkens and Michael Geerts. 

Spain and Australia were unable to progress but the hosts at least had the consolation of securing a victory thanks to wins for Jason Kubler against Albert Ramos-Vinolas, and the mixed doubles duo of John Peers and Sam Stosur against Jessica Bouzas Maneiro and David Vega Hernandez.

The USA had already secured their Finals berth against Great Britain in Sydney, but were ruthless as they finished off their tie against Germany to win 5-0.

After Jessica Pegula beat Laura Siegemund 6-3 6-2, Frances Tiafoe also defeated Oscar Otte in straight sets, before the American duo combined to beat Siegemund and Daniel Altmaier 6-7 (5-7) 6-4 10-7 to complete a clean sweep.

Boris Becker has swiftly found work after his release from prison, with the German tennis great signed up for television commentary during the Australian Open.

The six-time grand slam singles champion, who took the Australian title in 1991 and 1996, will be part of German Eurosport's team for the season's opening grand slam.

That was announced by the broadcaster on Tuesday, with Becker to co-commentate on big matches and present a 'Matchball Becker' analysis segment twice a day.

Becker, 55, has worked for Eurosport in previous years, as well as being a regular on the BBC's coverage of Wimbledon, a tournament he won three times.

He was released from jail in December, eight months into a two-and-a-half-year sentence handed down as punishment for hiding £2.5million worth of assets and loans to avoid paying debts when he was declared bankrupt in 2017.

Becker, a former coach of Novak Djokovic, 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.

In an interview with Sat.1 after his release, Becker spoke of his experience, saying: "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."

Novak Djokovic took just an hour and 15 minutes to win his first singles match in Australia since 2021, beating Constant Lestienne 6-3 6-2 at the Adelaide International on Tuesday.

Djokovic – who saw a three-year visa ban lifted in November – played with Vasek Pospisil in the doubles on Monday, but this was his first singles outing in the country since his vaccine-related absence from last year's Australian Open.

"For the first match [of the season] I can't complain," Djokovic said. "I played very well. I thought the first six games were very competitive and I have never faced him before.

"But once I made that break at 3-2 in the first set I thought I stepped it up and played really good tennis for the rest of the match."

Elsewhere in Adelaide, third seed Daniil Medvedev advanced after Lorenzo Sonego retired hurt with the Russian leading by a set, while sixth seed Jannik Sinner eased past Kyle Edmund 6-3 6-2.

Seventh seed Denis Shapovalov is also through after coming from a set down to beat Rinky Hijikata, but fourth seed Andrey Rublev is out after losing to Roberto Bautista Agut in three sets.

The Spaniard will face Sebastian Korda next after he beat Andy Murray 7-6 (7-3) 6-3, while eighth seed Karen Khachanov advanced after beating Pedro Cachin 6-2 6-4. 

At the Maharashtra Open in Pune, Aslan Karatsev had no problems seeing off Pablo Andujar 6-1 6-3, with the eighth seed set to face Tim van Rijthoven in the last 16 after the Dutchman beat Radu Albot 6-4 6-4.

There were also wins for Maximilian Marterer against Elias Ymer and Pedro Martinez against Ramkumar Ramanathan.

Rafael Nadal is "not too alarmed" about suffering back-to-back losses ahead of the Australian Open following his latest United Cup defeat.

The Spaniard suffered a second successive reverse in Sydney, going down 3-6 6-1 7-5 to Alex de Minaur after falling to Cameron Norrie.

Nadal is set to go in search of a record-extending 23rd grand slam title later this month, having won in Melbourne in 2022.

Yet the 36-year-old is not getting hung up on his form, instead taking the losses as learning curves.

"I have two weeks before the Australian Open starts," he said. "I can't say the situation is ideal, but I can't say it's negative.

"I was playing good. I need hours on court, I need battles like this. Days like these two help. I need to keeping fighting.

"I'm not too alarmed, too negative about what happened. I think it was a real chance to lose these kinds of matches."

Nadal won the first set against De Minaur, and was a game away from victory in the decider before succumbing to a comeback.

"Alex played better in the crucial moments. That made the difference," Nadal said.

"I had my chances to win, but I made costly mistakes when I could not afford them. You can not win a match like this while doing that."

Novak Djokovic was beaten in his first match back in Australia but did at least receive a warm reception from the crowd at the Adelaide International.

Djokovic – who saw a three-year visa ban lifted in November – was playing with Vasek Pospisil in the doubles, and the duo lost 4-6 6-3 10-5 to Tomislav Brkic and Gonzalo Escobar on Monday, but the fans in attendance chanted "Novak" as they welcomed him back following his absence from last year's Australian Open.

The Serbian will face Constant Lestienne in the first round of the men's singles, but second seed Felix Auger-Aliassime is already out after he lost to Alexei Popyrin.

Auger-Aliassime struggled throughout as his Australian opponent, ranked 120th in the world, put in a crowd-pleasing performance to go through 6-4 7-6 (7-5).

Another young star, Holger Rune, is also out after the fifth seed was beaten 2-6 6-4 6-4 by Yoshihito Nishioka.

Quentin Halys set up a potential second-round clash with Djokovic after beating Jordan Thompson in straight sets, while Miomir Kecmanovic, Jack Draper, Roman Safiullin and Thanasi Kokkinakis all progressed.

It was also a bad day for seeds at the Maharashtra Open in Pune, with Alex Molcan beaten 6-2 6-4 by Laslo Djere and Jaume Munar losing 6-4 7-5 to Tallon Griekspoor.

Dutchman Griekspoor will now play Marco Cecchinato after the Italian overcame Nikoloz Basilashvili, and Roberto Carballes Baena set up a last-16 clash against top seed Marin Cilic by defeating fellow Spaniard Bernabe Zapata Miralles.

Filip Krajinovic did make it through a tussle with home favourite Sumit Nagal to set up a meeting with Michael Mmoh, while Benjamin Bonzi will face third seed Emil Ruusuvuori after beating Tseng Chun-hsin.

Dan Evans helped Great Britain reach the last eight of the inaugural United Cup as his 6-3 1-6 6-3 win over Albert Ramos-Vinolas decided the team's Group D tie against Spain.

Rafael Nadal's shock defeat to Cameron Norrie – coupled with Katie Swan's win against Nuria Parrizas-Diaz – put Spain 2-0 down in the best-of-five tie ahead of Sunday's action.

World number 13 Paula Badosa put them back into contention with a hard-fought 6-7 (6-8) 7-6 (7-5) 6-1 win against Harriet Dart, but Evans gave Britain an unassailable lead by battling past Ramos-Vinolas, recovering from a dismal second set.

Having topped Group D, Britain will face the Croup C winners – the United States, Germany or the Czech Republic – for a semi-final place on Wednesday.

Meanwhile, Hubert Hurkacz doubled up to help Poland past Kazakhstan, teaming up with Iga Swiatek in the mixed doubles after beating Alexander Bublik.

Hurkacz beat Bublik 7-6 (8-6) 4-6 6-3 in just over two hours before Magda Linette overcame Zhibek Kulambayeva 6-2 6-1.

With Poland's first win in the competition secure, world number one Swiatek helped Hurkacz put the icing on the cake with a 6-3 6-4 victory against Kulambayeva and Grigoriy Lomakin.

The Czech Republic also enjoyed a fruitful day as two-time Wimbledon champion Petra Kvitova downed Laura Siegemund in straight sets to seal the team's win against Germany, but Casper Ruud was less fortunate, with Norway losing their tie against Brazil despite his success against Thiago Monteiro.

Wimbledon's ban on Russian and Belarusian players taking part last year was unjust and changed nothing regarding the war in Ukraine, believes Aryna Sabalenka.

Following Russia's invasion of Ukraine last February, the Lawn Tennis Association (LTA) barred players from both countries appearing at SW19 – a decision that saw the organisation fined by the ATP last month.

World number five Sabalenka joined the likes of Daniil Medvedev, Andrey Rublev and Victoria Azarenka in being excluded, and she believes the ban was both unfair and pointless.

"This is really terrible because no one supports war – no one," Sabalenka told The Age of the ban. "I'm just really disappointed sport is somehow in politics. 

"We're just athletes playing their sport. That's it. We're not about politics. If all of us could do something [about the war], we would do it, but we have zero control.

"They banned us from Wimbledon, and what did it change? Nothing. [The Russian government] are still doing this, and this is the sad part of this situation."

The LTA is yet to say whether similar measures will be in place this year, and Sabalenka is hopeful of a return after missing the atmosphere at SW19 in 2022.

"I really missed the people because the atmosphere at Wimbledon is super amazing," she said. "You can feel these people really love tennis there, and I really miss them.

"I really hope that I'll play there, just because of the people, to feel this atmosphere. If they're going to ban us again... I don't care about Wimbledon's decision. The only thing I'll miss is the people."

Rafael Nadal shot down questions over his potential retirement after losing to Cameron Norrie at the United Cup, saying he is "here to continue playing tennis".

As part of his preparation for next month's Australian Open, 22-time grand slam winner Nadal fell to a 3-6 6-3 6-4 defeat to Norrie as Great Britain seized a 2-0 lead over Spain in Sydney.

Norrie had not won a set against Nadal in their previous four matches, and the 36-year-old was asked afterwards how much longer he planned to continue before calling it a day on his historic career.

"Every time I come to a press conference, it seems like I have to retire," Nadal told reporters. "You're very, very interested in my retirement.

"At the moment, that's not the case. When this day comes, I'll let you know.

"But don't go on the subject of retirement because I'm here to continue playing tennis."

With just over two weeks until Nadal's Australian Open title defence gets underway, the Spaniard knows he will have to improve on his performance against Norrie, saying: "I need to be faster physically and a little more solid.

"There is a way to improve, but I have time before the Australian Open starts in two weeks."

While Nadal's shaky performance against Norrie could cause concern over whether he can defend his crown in Melbourne, he was keen to credit the British number one, stating: "He is a top player.

"He didn't impress me much because I know he is very good. He did a lot of things well, very solid, without mistakes, serving well. I can do things better and I need to."

Nadal will be in action again at the United Cup on Sunday, taking part in a doubles match with Paula Badosa against Daniel Evans and Harriet Dart.

Rafael Nadal's United Cup campaign began with defeat against Cameron Norrie as Great Britain established a 2-0 lead over Spain in Group D.

The 22-time grand slam winner surrendered a first-set lead before going down 3-6 6-3 6-4 against the world number 14, who secured his first victory in five meetings.

Norrie, who became only the second Briton after Andy Murray to beat the Spaniard, set the tone for his team, with Katie Dart also coming from behind to deny Nuria Parrizas Diaz 3-6 6-1 6-2 later on.

Meanwhile, Germany's Alexander Zverev lost in straight sets on his return to ATP action, going down 6-4 6-2 to Jiri Lehecka of the Czech Republic, who went 2-0 up in the tie after Marie Bouzkova defeated Jule Niemeier 6-2 7-5.

World number one Iga Swiatek got Poland off to a flying start against Kazakhstan in Brisbane with a commanding 6-1 6-3 victory over Yulia Putintseva, but defeat for Daniel Michalski against Timofey Skatov leaves the Group B tie finely poised.

Brazil enjoyed a flawless start against Norway in Group E. Beatriz Haddad Maia was a 6-4 6-2 winner over Malene Helgo, and Felipe Meligeni Alves overcame Viktor Durasovic 6-3 6-3.

The spoils were shared between Belgium and Bulgaria in Group A with Alison van Uytvanck beating Isabella Shinikova, before David Goffin was seen off by Grigor Dimitrov 6-4 7-5.

Croatia closed the day with a pair of victories against Argentina in Group F as Donna Vekic and Borna Coric defeated Maria Carle and Francisco Cerundolo respectively.

Alexander Zverev recognised his game remains below expectations after ending a six-month competitive absence, but the German is unconcerned as he continues his recovery.

The two-time ATP Finals winner suffered a serious ankle injury during the semi-finals of the French Open against Rafael Nadal, ruling him out of the rest of the 2022 season.

Though he has played in a number of exhibition matches since, Zverev only made his competitive return to action on Saturday at the United Cup in Sydney.

There, he suffered a 6-4 6-2 straight sets loss to the Czech Republic's Jiri Lehecka, though he was philosophical about his performance afterward.

"My tennis is far away from the level I want it to be," he said. "I think it is normal, not playing for seven months. There are things that are different than I'm used to.

"[Am I] concerned? Probably not. Physically, I'm not at the level that I have to be. This is not even a question. I'm getting tired a lot quicker than I did. I'm not as fast as I probably was.

"I don't think it will be a matter of tomorrow, [or] after tomorrow. It will be a few weeks until I'm back to the level I want to be."

Zverev, an Olympic gold medallist and US Open finalist, is anticipated to figure in next month's Australian Open, where he will be chasing a maiden grand slam trophy.

The German is focused on reaching full fitness rather than putting undue pressure on himself, though, adding: "I think it's tough to set expectations right now.

"It would be unrealistic and quite stupid for me to set the expectations towards winning or something like that.

"Of course, I want to win. Everybody wants to win. [But] for me, it's about getting back the form that I'm used to."

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.