Martina Navratilova has been diagnosed with throat and breast cancer, though a representative described the prognosis as "good".

Navratilova won 18 grand slam singles titles between 1978 and 1990, making her one of the most decorated players of all time.

She underwent successful treatment for breast cancer in 2010, but it has now been confirmed she is battling the illness again.

Navratilova said: "This double whammy is serious but still fixable, and I'm hoping for a favourable outcome.

"It's going to stink for a while but I will fight with all I have got."

Navratilova, 66, was due to travel to Melbourne this month to work on coverage of the Australian Open, a tournament she won three times.

But with her treatment due to start later in January, it has been confirmed she will not be in attendance.

A statement from a representative explained: "The prognosis is good and Martina will start her treatment this month.

"The cancer type is HPV and this particular type responds really well to treatment.

"Martina noticed an enlarged lymph node in her neck during the WTA finals in Fort Worth. When it didn't go down, a biopsy was performed, the results came back as stage one throat cancer.

"At the same time as Martina was undergoing the tests for the throat, a suspicious form was found in her breast, which was subsequently diagnosed as cancer, completely unrelated to the throat cancer.

"Both these cancers are in their early stages with great outcomes.

"Martina won't be covering the Australian Open for Tennis Channel from their studio but hopes to be able to join in from time to time by Zoom."

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.

Rafael Nadal suffered his second defeat in as many matches after going down 3-6 6-1 7-5 against Alex de Minaur at the United Cup.

The 22-time grand slam champion, who was also beaten by Great Britain's Cameron Norrie in his opening match, is still seeking his first victory of the season with the Australian Open just around the corner.

Home favourite De Minaur delighted the Sydney crowd by recovering from a set and break down to claim his maiden win over the world number two.

"I think it's definitely up there [as one of my best wins]," he said. "It's one of those achievements that you have unlocked in your career.

"But also, it's a big win for myself, one that I really needed. I'm going to cherish and use, take all the confidence from this and be able to hopefully take it to have a good [Australian] summer."

Spain and Australia are unable to progress to the City Finals, but Nuria Parrizas Diaz levelled the Group D tie with a 6-1 6-3 victory over Maddison Inglis.

The USA, who required just two points against Germany to advance to the next stage, set up a showdown with Great Britain after Taylor Fritz and Madison Keys enjoyed straight-set successes over Alexander Zverev and Jule Niemeier respectively. 

Italy moved to the brink of joining them in the City Finals after taking a 2-0 lead over Norway. Lorenzo Musetti overcame Viktor Durasovic in straight sets, while Martina Trevisan edged out Malene Helgo in three.

Greece require one win from their final three matches against Belgium to also advance, Stefanos Tsitsipas hit 12 aces on the way to defeating David Goffin 6-3 6-2 to level the Group A showdown at 1-1.

Poland's winner-takes-all Group B clash with Switzerland is also finely poised at 1-1. World number one Iga Swiatek beat Belinda Bencic 6-3 7-6 (7-3), before Marc-Andrea Huesler's 6-3 6-2 victory against Daniel Michalski.

Linda Noskova produced the biggest win of her career as she defeated Daria Kasatkina 6-3 6-7 (2-7) 6-3 at the Adelaide International on Monday.

The 18-year-old Czech was impressive against the third seed as she recorded her first win against anyone in the top 30 of the world rankings.

Fourth seed Veronika Kudermetova eased past Amanda Anisimova in just an hour and 15 minutes, winning 6-3 6-0, while Liudmila Samsonova will face second seed Aryna Sabalenka in the next round after coming from a set down to beat Zhang Shuai 5-7 6-3 6-0.

Irina-Camelia Begu and Elena Rybakina also both came from behind to secure wins, with the latter beating fifth seed Danielle Collins to set up a last-16 clash against Ukrainian Marta Kostyuk, who beat Jaimee Fourlis 6-1 3-6 6-4.

At the ASB Classic in Auckland, 42-year-old Venus Williams comfortably overcame her 21-year-old opponent Katie Volynets 7-6 (7-4) 6-2, and will play China's Zhu Lin next after she eliminated sixth seed Madison Brengle 4-6 7-6 (8-6) 6-4.

Third seed Leylah Fernandez beat Brenda Fruhvirtova 6-1 6-1 to set up a last-16 tie with Julia Grabher after she defeated Tereza Martincova in three sets.

Eighth seed Rebecca Marino is through after beating Dalma Galfi in straight sets and will now face Ysaline Bonaventure, who eventually put away Caty McNally 5-7 6-4 6-4.

Viktoria Kuzmova led fourth seed Bernarda Pera 5-4 in the opening set when rain stopped play for the day.

Roger Federer saluted Iga Swiatek's miracle shot at the United Cup, declaring 'that was crazy' in response to a tweet from the world number one.

Swiatek - the winner of eight WTA titles in 2022 including the French Open and US Open - helped Poland to a commanding 4-1 victory over Kazakhstan in their opening match in Brisbane.

With the Poles' first win in the competition secure, the 21-year-old helped Hubert Hurkacz put the icing on the cake with a 6-3 6-4 success in their mixed doubles clash against Zhibek Kulambayeva and Grigoriy Lomakin.

Swiatek's moment of brilliance came at 30-15 in game six. Desperately chasing Lomakin's drop volley after a fiercely contested rally, she produced a wonderful backhand slice around the net post to the amazement of everyone inside the Pat Rafter Arena.

The shot was executed on several occasions by 20-time grand slam champion Federer, who retired last year, including in his third-round clash with Nick Kyrgios at the 2018 US Open.

Swiatek subsequently asked the Swiss in a light-hearted tweet: "Do you approve?" - to which he replied: "That was crazy."

The world number one is back in action on Monday when Poland ironically face Switzerland, who boast the likes of Olympic gold medallist Belinda Bencic and three-time grand slam winner Stan Wawrinka in Group B.

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.

Iga Swiatek warned rivals "I'm getting stronger and stronger in my mind" as she targets another memorable season in 2023.

The world number one enjoyed a dominant 2022 as she landed eight titles, including the French Open and US Open, while also embarking on a 37-match winning streak – the longest this century on the WTA Tour – and registering 22 'bagel' sets.

Swiatek made a winning start to her 2023 campaign at the United Cup with Poland earlier in the week, beating Kazakhstan's Yulia Putintseva 6-1 6-3 in Brisbane.

While acknowledging she must not become complacent this year and rely on past glories, the 21-year-old feels better prepared for the season with the Australian Open just a fortnight away.

"I feel more solid, and I feel more stability as well because last year, Adelaide was my first tournament with a new coach [Tomasz Wiktorowski], so that was my main focus," she said.

"This year, I have totally different challenges, so it's really hard to compare. But I feel like I had more time to actually work on some technical stuff at home, and hopefully I'm going to be able to use it in matches.

"I just think that it's going to be pretty easy for my head to compare everything to last year. And I feel like it's not really going to be helpful.

"Last year, it wasn't perfect, but sometimes when you win tournaments, all your head can remember is those good moments and that it went so smoothly.

"It wasn't like that, but I don't really want to go into those tournaments and be held back by my previous results. I want to treat it as new chapters, so I'm going to try to do that.

"But this is the biggest challenge I'd say, and we'll see how I'm going to go with that. Usually when I had goals like that, I had ups and downs, but I feel like I'm getting stronger and stronger in my mind, so maybe I'm going to be able to control that."

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.

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.