Andrey Rublev became the first Russian to win the Mubadala World Tennis Championship by beating Andy Murray in straight sets on Saturday.

World number five Rublev secured a 6-4 7-6 (7-2) victory over the three-time grand slam champion in the final in Abu Dhabi.

Murray had beaten Rafael Nadal in the exhibition event, but was unable to end the year on a high note.

Rublev claimed the only break of a tight first set and dominated a second-set tie-break after Murray had fought back from failing to hold in the opening game.

Murray had been given a way back into the contest when Rublev threw in three double faults in the eighth game of the second set to be pegged back at 4-4, but was unable to force a decider.

Nadal suffered another loss as he works his way back from injury, with Denis Shapovalov coming from a set down to beat the legendary Spaniard 6-7 (4-7) 6-3 10-6.

Rafael Nadal declared his Abu Dhabi mission a success despite suffering a second consecutive defeat at the Mubadala Tennis Championship on Saturday.

After a hard-fought battle with Andy Murray on Friday served up a reminder of many a classic match between the pair, it was Denis Shapovalov who beat Nadal in his second comeback clash.

Since losing to Novak Djokovic in the French Open semi-finals in June, Nadal had played only two matches due to a worrying foot injury.

That has been a long-term problem and the 35-year-old Spaniard chose this week's event to test how it would stand up to match conditions.

Canadian Shapovalov beat his fellow left-hander 6-7 (4-7) 6-3 10-6, but Nadal has done enough in his two matches, and in a practice session with Andrey Rublev, to be persuaded his prospects for 2022 are looking up, with the Australian Open just a month away.

The 20-time grand slam champion said: "Maybe it was too tough to start after a long time."

But he was laughing as he said that, and added: "The goal is achieved: to be back on court. I've played two matches and played more or less four hours on court.

"I enjoyed it. Congrats to Denis today. I wish you all the very best for the next season, and I'm going to try to keep going with my road."

Nadal said he would return to the tournament in future years, as long as he remains fit and still on tour.

"If I'm still playing tennis, I am always super happy to be here playing," he said. "Hopefully I can keep coming during the next couple of years."

Shapovalov, 22, is one of the ATP Tour's most talented youngsters, striving to make a telling impact while the likes of Nadal, Novak Djokovic and Murray reach the twilight years of their careers.

He said of Saturday's win over Nadal: "Any time I get to go on court against a guy like Rafa is an honour for me.

"It's great to just see you back on the court and see you healthy. Hopefully you can grab a great season and keep going."

Dominic Thiem's comeback has been further delayed as the 2020 US Open champion does not feel ready to return at this week's Mubadala World Tennis Championship.

Austrian star Thiem has been out of action since suffering a wrist injury at the Mallorca Championships in June.

The 28-year-old missed Wimbledon and was unable to defend his title at Flushing Meadows, but he appeared to be on course to make his comeback before the end of 2021 after revealing in October he does not require surgery on his wrist.

However, the world number 15 is now facing a battle to be back to full fitness for January's Australian Open after withdrawing from an exhibition event in Abu Dhabi.

"I was looking forward to making my return to competition at Abu Dhabi but I feel that I am not yet ready to compete at the highest level," the 17-time ATP Tour champion posted via Twitter on Tuesday.

"It's disappointing to not take part this year but I need to continue my preparation for the upcoming season."

Thiem follows Casper Ruud in pulling out of the tournament, which begins on Thursday, while Emma Raducanu is out of the women's singles after testing positive for coronavirus.

Dan Evans and Taylor Fritz have taken the places of former world number three Thiem and Ruud, joining Andrey Rublev, Denis Shapovalov, Andy Murray and defending champion Rafael Nadal in the draw.

US Open champion Emma Raducanu will miss this week's Mubadala World Tennis Championship after testing positive for coronavirus.

The 19-year-old had been due to take on Tokyo Olympics gold medallist Belinda Bencic in the exhibition event in Abu Dhabi.

However, Raducanu announced on Monday that she will not be able to take part in the tournament as she is now self-isolating. 

"I was very much looking forward to playing in front of the fans here in Abu Dhabi, but unfortunately after testing positive for Covid-19, I will have to postpone until the next opportunity," Raducanu said.

"I'm isolating as per rules and hopefully will be able to get back on court soon."

Raducanu became the first qualifier to win a grand slam title with victory at Flushing Meadows in September, but she has won just two of her five matches since then.

The British teenager, who recently appointed Torben Beltz as her new coach after parting company with Andrew Richardson, will next be in action at the Melbourne Summer Set early in the new year as preparation for the Australian Open.

Rafael Nadal intends to make his Tour comeback next month and plans to play at the 2022 Australian Open.

The 20-time major champion has not played since a defeat to Lloyd Harris at the Citi Open in August.

The 35-year-old, who withdrew from Wimbledon and the Tokyo Olympics after losing to Novak Djokovic in the French Open semi-finals, also pulled out of the US Open due to a recurring foot injury.

Nadal has spent time training in Mallorca this month following treatment in Barcelona and said he was not sure when he would make his return to action.

Speaking at a sponsor event in Paris, Nadal said he hopes to play at the World Tennis Championship next month before a possible tilt at the first grand slam of next year, an event he has won just once back in 2009.

"My plan is to play Abu Dhabi in December and then in a tournament before Australia and then the Australian Open. That's my goal," Nadal said. "We're working hard to make it happen.

"The injury in my foot still needs to get a little better, but I'm already training almost an hour and a half a day so that's positive. Some days are better than others, but I'm starting to have a lot more positive days than negative ones.

"So, I'm on the right track. I'm training, I'm feeling better. I'm back on the court."

World number eight Casper Ruud and world number 13 Denis Shapovalov are two of the big names from the ATP Tour to have confirmed they will play in Abu Dhabi in the event that runs from December 16-18.

Women's Olympic gold medallist Belinda Bencic and surprise US Open champion Emma Raducanu have also signed up to make their tournament debuts.

The Australian Open, won this year by Novak Djokovic, is due to start on January 17.