The new tennis season starts this week with the inaugural United Cup in Australia.

Before the first ball of the season is hit, we consider what the big tennis questions for 2023 might be and ask BBC tennis correspondent Russell Fuller for his verdict.

Rafael Nadal won two Grand Slam titles in 2022, taking his tally to a men's record 22 major singles trophies.

It was something of a resurgence for the 36-year-old - he had not won back-to-back Grand Slams for 12 years - and his 14th French Open title came despite having "no feeling" in his left foot as he was having multiple injections to numb chronic foot pain.

After the victory in Paris he had a nerve-burning treatment so that he could avoid further jabs and he went on to reach the Wimbledon semi-finals before withdrawing with an abdominal injury.

He shed tears in September when he played alongside Roger Federer as the Swiss called time on his career and while Nadal's mind clearly wants to continue playing tennis at the highest level, it seems that his body is becoming increasingly reluctant and it may not be too long before he follows his great rival into retirement.

Nadal will play at the United Cup so we should get an early clue as to what his physical condition looks like before he defends his Australian Open title.

Russell Fuller's verdict: Not entirely, I suspect, but Nadal proved last year he can still win Grand Slams in between rest periods. And he is a past master at getting himself fit for the second week at Roland Garros.

A year ago Novak Djokovic was deported from Australia before he could begin the defence of his title after his visa was cancelled in a row over his Covid-19 vaccine status.

He was automatically banned from entering the country for three years but that has been overturned and the former world number one will now return to Melbourne seeking a record-extending 10th title.

The saga dominated the headlines in the build-up last year, splitting public opinion, and it is unclear what kind of reception the Serb will get when he walks out on court. Tournament director Craig Tiley said last month he expected the crowd to be "fair".

Russell Fuller's verdict: My hunch is quite a good one. I'm sure there will be some anger on radio phone-ins as he arrives in the country, and a few larrikins in the stands come the Australian Open, but he is a nine-time champion who can win those fans over.

Three out of the four men's major titles were won by Nadal and Djokovic in 2022, continuing a pattern of recent years - the pair have won 15 of the past 18 Grand Slam titles.

But the past three editions of the US Open have been won by different players, with Dominic Thiem, Daniil Medvedev and Carlos Alcaraz winning their maiden Grand Slam titles in New York.

Nadal has question marks over his fitness, Djokovic is short of match practice after his vaccination status ruled him out of various events in 2022 and Federer has retired, which may open the door for some new champions.

Denmark's Holger Rune put himself firmly in the conversation by coming from behind to beat Djokovic in the final of the prestigious Paris Masters final in November and the 19-year-old has set his eyes on more.

"I know what I want," he said. "I want to win Slams. I won an ATP 250, reached an ATP 500 final and won a Masters 1,000. It's time for a Slam win."

Norwegian 23-year-old Casper Ruud, runner-up at the French and US Opens in 2022, will be hoping to go one better, while Australian Nick Kyrgios, 27, will be aiming to carry on the momentum he built with a Wimbledon final appearance and a US Open quarter-final.

In the women's game, Tunisia's Ons Jabeur will be keen to take one of the big prizes after back-to-back finals in the last two Grand Slams of last season.

Russell Fuller's verdict: Ons Jabeur and Casper Ruud now have Grand Slam final experience and a very high seeding and I don't see any reason why they can't take the final step. And, more speculatively, could China's Zheng Qinwen or even 17-year-old Czech Linda Fruhvirtova go the distance?

Wimbledon organisers were fined for their decision to ban Russian and Belarusian players from the grass-court Grand Slam this year because of Russia's invasion of Ukraine.

There is no end in sight to the war so Wimbledon is likely to face a sensitive decision in the coming months about whether to continue to ban the players.

The men's ATP Tour and women's WTA Tour also stripped Wimbledon of ranking points in response to the ban and while last year players were still attracted to the event, it could become less appealing to them if there are no points once again.

Russell Fuller's verdict: The All England Club will be extremely anxious to avoid a repeat of last year and return the championships to full strength. But it will still be very difficult for them to ignore any strong governmental direction (whether public or otherwise) to ban Russian players.

Emma Raducanu's first full year on the tour was frequently interrupted by injuries and coaching changes, with the 20-year-old Briton unable to build on her stunning 2021 US Open success with more titles.

In a bid to make herself less prone to injury, she has been working with physical trainer Jez Green, who played a key role in Andy Murray's physical development early in his career.

"My biggest goal in 2023 is to be more injury free," she told lifestyle magazine SheerLuxe earlier this month.

"This year, the demands of the tour, going from having no training or stamina to being thrown into competing at the top level, my body has struggled.

"So, I'll be working hard to keep my body in good shape and improving. If you want a 'resolution' it's probably to be consistent. Put in the work, day in, day out."

Russell Fuller's verdict: The omens are more encouraging. Despite the wrist injury she took into pre-season, Raducanu has had a much better training block. She avoided Covid this year, and looks set to share Jez Green with Dominic Thiem on tour next year.

This year marked a breakthrough season for 21-year-old Briton Jack Draper, who rose to a career-high world number 41 from 265 at the start of the year.

He reached the Eastbourne semi-finals and an ATP 1,000 quarter-final in Canada, was well as the Next Gen Finals, which are for the Tour's best players aged 21 and under.

Victories against top-10 players Stefanos Tsitsipas and Felix Auger-Aliassime, as well as former world number three Dominic Thiem, showed he can compete at the highest level and makes him one to watch in 2023.

Russell Fuller's verdict: Finishing the year in the top 20 would be fantastic, and not implausible. He starts the year at 42 - trying to halve your ranking in a season is always a good target for aspiring young players.

It's not entirely impossible.

Since a farewell ceremony at the US Open in September following the 41-year-old's announcement she was "evolving away" from tennis, the American 23-time Grand Slam singles champion has maintained that she is "not retired".

And last month she posted a photo of a tennis racquet in plastic wrapping with the words "I'm a little bored".

Surely, she couldn't?

Russell Fuller's verdict: No. But I am sure she will think about it in the spring with Wimbledon and the US Open fast approaching.