Rafael Nadal has turned down a wildcard invitation to compete in next week's Dubai Tennis Championships as he does not feel ready to return to action.

The world number two has been struggling with a lower back injury sustained prior to the Australian Open, which he exited in the quarter-finals at the hands of Stefanos Tsitsipas.

Nadal has not competed since, having subsequently pulled out of the ATP Cup and Rotterdam Open after being advised to give his back time to heal.

And the 20-time grand slam winner will delay his return for a little while longer after deciding to skip the upcoming ATP 500 event in Dubai.

"I would like to thank the @DDFTennis for the wild card invitation sent to me," Nadal posted on his Twitter page on Thursday. 

"We seriously thought about coming to play, but I don't think I am ready to play yet. Once again thanks to the tournament's kind invitation and best of luck with the tournament."

The Spaniard added in a later tweet: "And special thanks to Tournament Director Salah Talak since I am aware of his efforts to ensure a smooth arrival to play Dubai during this unprecedented Coronavirus pandemic and difficult times for all."

Nadal won his only Dubai Tennis Championships title in 2006 with victory over Roger Federer – the competition's record eight-time winner – in the final.

Federer is scheduled to take part in this year's tournament after making his long-awaiting return from a 14-month injury lay-off at the Qatar Open this week.

Garbine Muguruza made light work of Iga Swiatek to book her place in the quarter-finals of the Dubai Tennis Championships.

The in-form Spaniard required just one hour and nine minutes to win 6-0 6-4 against the number eight seed and reach the final eight for the fourth time in seven appearances at the tournament.

Reigning French Open champion Swiatek came into the contest on a six-match winning streak but her resistance seemed to falter after she dropped serve in the opening game and then failed to capitalise on two break points in the second.

Muguruza, whose 2021 record now stands at 15 wins and four defeats, was comparatively ruthless against an opponent who landed with just 38 per cent of her first serves.

The former world number one and double grand-slam champion let a 3-1 lead slip in the second set before resuming control through her punishing forehand, getting the job done on the first match point with an ace.

She will be back into action on Thursday against Aryna Sabalenka. The Belarusian, who beat Anett Kontaveit 6-3 6-2, lost in three sets to Muguruza at the Qatar Open last week.

"Back-to-back matches is good," said Muguruza. "That means I'm playing the top players, that means I'm getting into the deep rounds. I'm looking forward for another battle."

Coco Gauff reached the last eight of a WTA 1000 event for the first time after a straight-sets win over qualifier Tereza Martincova.

The American, who turns 17 on the day of the final, won 6-4 6-2 to set up a showdown with Jil Teichmann, a 6-3 6-3 winner over Ons Jabeur.

Second seed Karolina Pliskova was a surprise casualty, losing in less than an hour to Jessica Pegula. The world number 36, who also beat Pliskova in Qatar, will face Elise Mertens after she beat Caroline Garcia 6-4 6-2.

The last remaining former champion in the draw, Belinda Bencic, suffered disappointment on her 24th birthday as she lost 6-1 2-6 7-5 to wildcard Anastasia Potapova. She will take on Barbora Krejcikova, who eliminated Svetlana Kuznetsova.

Dan Evans is putting friendship aside after earning a blockbuster showdown against returning superstar Roger Federer at the Qatar Open.

Federer has not played competitively since his semi-final exit at the 2020 Australian Open – the 20-time grand slam champion having undergone knee surgery last year.

But the 39-year-old Swiss great will make his long-awaited comeback against Evans in Doha on Wednesday.

Evans – who has been practicing with Federer – outlasted Frenchman Jeremy Chardy 6-4 1-6 6-2 in the round of 32 at the ATP 250 tournament.

"We obviously practised for [the] past two weeks [in Dubai], and I thought he was playing pretty well," Evans said. "We played plenty of sets. It was competitive. But it's all very different when you get on the match court.

"It will be a lot different tomorrow. It's going to be at night, as well, so a little slower. So we'll see how the match goes."

Second seed Federer – a record three-time Qatar Open champion – watched from the stands on Tuesday and Evans added: "He obviously has seen a lot of my game the past few weeks, so I guess I would say it was more out of boredom.

"He's probably [was] waiting for his practice [more] than scouting out what's happening on the court. Let's put it down to that."

Elsewhere, sixth seed David Goffin topped Filip Krajinovic 6-4 6-4 en route to the last 16 but three-time slam champion Stan Wawrinka was stunned 7-6 (7-3) 6-7 (6-8) 7-5 by qualifier Lloyd Harris.

Marton Fucsovics, Vasek Pospisil and Malek Jaziri also advanced through to the next round.

At the Open 13 Province, three-time champion and French veteran Jo-Wilfried Tsonga celebrated his first ATP Tour victory since 2019.

Tsonga – hampered by injuries, including left knee surgery –rallied from the brink to see off Feliciano Lopez 3-6 6-4 7-5 in Marseille on Tuesday.

"This is probably one of the best victories of my career, because it was tough for me to play tennis. I had so much pain for so many months," Tsonga said in an on-court interview. "Today, I won one match. That was one of my goals for these few weeks… I’m happy like a kid."

Next up is fourth-seeded countryman Ugo Humbert, who upstaged sixth seed Kei Nishikori 6-1 6-4.

Meanwhile, Federico Coria and Federico Delbonis were among the victors at the Chile Open.

Roberto Bautista Agut rallied from a set down to defeat Reilly Opelka 4-6 6-3 6-4 in the first round of the Qatar Open.

Bautista Agut, who is the fifth seed in a draw featuring Dominic Thiem, Roger Federer and Andrey Rublev, was the highest ranked player in action in the round of 32 and fell behind to world number 39 Opelka.

Yet, the Spaniard pulled out his familiar battling qualities to prevailed over the big-serving American, who held sway 22-6 in the aces count.

Nevertheless, Bautista Agut was still able to fashion 11 break points over the course of the contest, converting one apiece decisively in sets two and three.

Alexander Bublik took the notion of big serves not being a decisive factor to an extreme as he popped in an underarm to fine effect on match point – qualifier Ramkumar Ramanathan scampering to thump his return out and conclude a 6-4 6-2 loss against Bautista Agut's next opponent.

The match between world number 42 Nikoloz Basilashvili and 41John Millman was as close as the rankings suggested, with the Georgian coming back to win 2-6 6-4 6-2.

Richard Gasquet and Taylor Fritz were straight-sets winners, with Rublev up next for Gasquet.

At this week's other ATP 250 event, the Open 13 Provence in Marseille, eighth seed Yoshihito Nishioka bowed out when he retired 2-6 2-4 down to Emil Ruusuvuori.

Wildcard Hugo Gaston beat Dennis Novak 3-6 6-4 6-1 to claim a notable scalp.

Top seed Daniil Medvedev, Stefanos Tsitsipas, Karen Khachanov and Ugo Humbert will enter the fray in the last 16.

Dominic Thiem is relishing Roger Federer's return to action, with the duo taking part in this week's Qatar Open.

Federer has spent the last 13 months out, having elected to take 2020 off – following last year's Australian Open – to undergo two knee operations.

The 40-year-old will compete in Doha this week, returning to play in an event where he has enjoyed plenty of success down the years, winning the tournament three times.

Last year's US Open champion Thiem, who has moved above Federer in the world rankings during the Swiss' absence, will also be in action in Qatar, and is thrilled to see the 20-time grand slam winner make his comeback.

"We are rivals, and of course we want to beat each other in the tournament, [but] I still really love to watch him play tennis," said top seed Thiem, who was speaking to Laureus Sport after his nomination for Breakthrough of the Year.

"[He] looks so nice, the way he plays, the way he approaches the game of tennis.

"On the one hand, I'm also a big fan of his still, and that's why I really love that he's back and that I can watch him again. That's what pretty much everybody is thinking, and I hope that he's coming back strong, as well."

Federer and Thiem have met seven times, with the Austrian holding the advantage, with five wins to his name against the former world number one.

Thiem, a semi-finalist in Doha in 2018, has not played since he lost to Grigor Dimitrov at the Australian Open in mid-February, and the world number four is hoping to make a fast start when he takes on Aslan Karatsev in round two.

"The [Doha] draw is unbelievably strong, so [you] never know what's [going to] happen, but I just try to have a good start and to be there on a good level from the very first point," said Thiem.

"It's going to be my first tournament and [my] first match [in almost] a month, since [a] pretty devastating loss at the Australian Open.

"I needed some time to digest everything, to analyse everything [and] to settle down a little bit. Now it's time to focus on new things. The tournament in Doha is the first chance to play better again, to get good results, to get confidence and to forget a pretty tough start of the season."

Elena Rybakina, the 2020 finalist, eased through her Dubai Tennis Championships opener on a second day dominated by the seeds.

Rybakina was beaten in last season's Dubai decider by Simona Halep, one of five WTA Tour finals she reached in a breakout year.

The Kazakh, with two career titles to her name, has not played a final since September, however, and entered this week's tournament with a 4-4 record for 2021.

But her fine form in Dubai continued with a straightforward first match, beating Zheng Saisai 6-0 6-4 in 73 minutes.

"I lost a bit of concentration in the second set," number 14 seed Rybakina said. "Also Saisai played well - she decided to risk stepping in on the returns - so overall I think it was not a bad match."

Garbine Muguruza also built on a final defeat, having come up short in Saturday's Qatar Open decider, thrashed by Petra Kvitova.

Including that event, Muguruza has reached the showpiece match at two of the four tournaments she has entered prior to this latest campaign, which began with a 6-3 7-5 win over Irina-Camelia Begu.

Fellow seeds Madison Keys, Marketa Vondrousova and Anett Kontaveit each also raced through in straight sets.

Petra Martic could not join them, however, going down 7-6 (7-2) 6-4 to Kristina Mladenovic.

Meanwhile, Jessica Pegula continued her rich vein of form in a dominant 6-2 6-1 defeat of Yaroslava Shvedova.

The American reached the quarter-finals of the Australian Open and the last four as a qualifier in Qatar, meaning she is now 11-2 since heading to Melbourne.

One-time French Open winner Jelena Ostapenko also triumphed, while former Roland Garros semi-finalist Amanda Anisimova, still just 19, made a victorious 2021 WTA bow.

But three-time grand slam champion Angelique Kerber continues to struggle for momentum, letting a set lead slip to lose to Caroline Garcia.

Former world number one Roger Federer said he has no real expectations for his comeback event at the Qatar Open.

Federer has not played competitively since his semi-final exit at the 2020 Australian Open – the 20-time grand slam champion having undergone knee surgery last year.

The 39-year-old Swiss superstar opted not to travel to Melbourne for this year's Australian Open, but he is set to make his comeback in Doha.

Federer, who holds the record for most Qatar Open titles with three – will start his campaign against either Jeremy Chardy or Daniel Evans at the ATP 250 tournament.

"It's been a long year in some ways, especially rehabbing, being on crutches once and then for a second time, and finally I'm back on a tennis court again, working out, playing sets, playing points," Federer said.

"It's a true pleasure, it's a privilege actually after all this time. I didn't expect it to go as long as it did, we are where we are, I'm so excited to be back on a match court, you know, in a few days here.

"I'm really curious to find out how it's going to go, obviously there's an amazing amount of questions marks surrounding my comeback for me personally.

"I don't know what to expect, I know that expectations from myself are extremely low, and I'm just very happy that I'm playing a tournament again, regardless of the outcome of this event."

On whether he had doubts over returning, Federer added: "You always do have doubts, you know, when you have surgery, there are always days when you feel better and worse. But I think overall I am a very positive person, I have a great team around myself, my family, I am also very distracted, and you know, the idea was to be fully fit again, one day. For life or for tennis.

"So equally important to me, actually life is a little bit more important to me, I wanna go skiing and play basketball, I wanna go playing ice hockey, play tennis in the future, with my children or exhibition matches, you name it, so it's definitely worth it to go through all that pain you know. But the goal was, this is not I'm going to go out, I'm not happy with my knee, we're going to fix it, and then I'm going to come back.

"For me there was no other story to it, and rehab wasn't as hard as maybe people make it seem, even though people around me are very impressed how I go about it, but for me it's only but normal to be really, really professional about it."

Novak Djokovic made history after breaking Roger Federer's record for most weeks as world number one on the ATP Tour.

Djokovic surpassed Federer after beginning his 311th week as the number one player in the men's rankings on Monday.

Serbian star Djokovic reclaimed the top ranking from fellow superstar Rafael Nadal in February 2020 and finished as year-ending number one for the sixth time – tying the mark set by Pete Sampras.

Djokovic, who first topped the men's rankings in July 2011, went on to celebrate a record-extending ninth Australian Open title at Melbourne Park in February.

With Federer turning 40 in August and Nadal a year older, the 33-year-old Djokovic has time on his side in pursuit of more history.

Djokovic has won 18 grand slams, two adrift of Federer – who is set to make his long-awaited ATP comeback in Qatar this week – and Nadal.

"I think it's an ultimate challenge to be honest, of course, winning a slam and being in history, the longest-ever number one," Djokovic said in Melbourne last month.

"You can have a great grand slam, a great tournament, a great couple of months, or even a great season but to do it over and over again, to be actually contender for historic number one, you need to play well and have a consistency from January to November, ever single year.

"I've been fortunate to do that and put myself in a position to make history in that regard. I'm very, very proud of that and privileged to be in that position.

"It's also a relief because it has been definitely my main goal, other than winning slams and now that I'll be managing to achieve it, I'll focus myself more on slams and adapt my calendar and schedule because when you're going for number one, you have to play all year and you have to play all the biggest tournaments.

"You can't allow someone else to earn more points than you. It's like a constant pressure, I think, and expectations that you have to deal with. It's definitely fulfilling to achieve that."

Federer now sits sixth in the rankings, having not played competitively since the 2020 Australian Open.

Nadal remains second, though he is set to be leapfrogged by Australian Open runner-up Daniil Medvedev in the next rankings release on March 15.

Russian Medvedev will be the first player, other than Djokovic, Nadal, Federer and Andy Murray, ranked in the top two since July 2005.

Diego Schwartzman claimed his first ATP Tour title on home soil as he defeated qualifier Francisco Cerundolo in the final of the Argentina Open on Sunday.

After losing in his two previous finals in Argentina, Schwartzman finally came good in his home city of Buenos Aires with a 6-1 6-2 victory. 

The world number nine was in complete control from the off, breaking six times and conceding on his serve just once as he took just 81 minutes to wrap up a fourth Tour title.

Cerundolo's run to the final had at least ensured that whoever came out on top in the showdown would result in the first Argentine champion of the competition since 2008, when David Nalbandian triumphed in a clash with compatriot Jose Acasuso.

"I'm very, very happy, it's been an amazing week for me," Schwartzman said in the trophy presentation.

"It's the first time that [I have won at] home. Two years ago, I reached the final here and lost. I was very unhappy, but two years later I have my revenge against Francisco who is a great player."

Danish teenager Clara Tauson landed a first WTA Tour title as the former junior world number one triumphed at the Lyon Open on Sunday.

The 18-year-old beat Swiss opponent Viktorija Golubic 6-4 6-1 in a final contested by two qualifiers, achieving her breakthrough win in an hour and 29 minutes.

Golubic saved five match points but eventually was put away by Tauson, who has spent most of her senior career to date on the second-tier ITF tour.

She caused a major shock at the French Open in September by beating US Open semi-finalist Jennifer Brady in the first round, and Tauson should now become a more familiar presence at the higher level.

The win carries the youngster into the WTA top 100 for the first time, and it completed an impeccable trip to France that saw Tauson win all seven of her matches, including two qualifying rounds, in straight sets.

She said of her performance: "I think I've been really solid; especially after the first set, I've come out good in every single match."

Quoted on the WTA website, Tauson added: "I just kept my game going. It's been a weird week like that, normally I have some fall-outs, but I haven't had any of those this week, so I'm very happy with that."

Tauson shocked Russian top seed Ekaterina Alexandrova in the first round at the start of the week in Lyon, and Alexandrova lost to another teenager on Sunday as the Dubai Tennis Championships began.

The world number 33 was handed a tough draw against American Coco Gauff, who scraped through 7-6 (7-3) 2-6 7-6 (10-8) in a match lasting two hours and 41 minutes.

Gauff served 12 double faults, including seven in the deciding set, but found a way through to the second round.

Svetlana Kuznetsova, Ons Jabeur and Alize Cornet were among the other winners on day one. The top eight seeds, who include Iga Swiatek, Karolina Pliskova, Elina Svitolina and Petra Kvitova, have all received byes to round two of the WTA 1000 event.

Andrey Rublev maintained his magnificent form by beating Marton Fucsovics in straight sets to win the Rotterdam Open.

Rublev won Sunday's final 7-6 (7-4) 6-4 to claim his fourth consecutive ATP 500 title.

The world number eight from Russia has now won 13 of his 14 matches this year, his only defeat coming against Daniil Medvedev in the quarter-finals of the Australian Open.

Rublev won 75 per cent of points on his first serve, winning the first set on a tie-break after saving four break points in the opening game.

Fucsovics was unable to turn it around in the second set, Rublev claiming his second win in three meetings with Fucsovics.

Just the one break in the opening game of the second set was enough for Rublev to add to his victories in Hamburg, St. Petersburg and Vienna last year.

World number 10 Petra Kvitova says Doha feels like home after taking out her second Qatar Open title in her third final in four years over Garbine Muguruza in Saturday's final.

Kvitova needed little over an hour to get past 16th-ranked Muguruza 6-2 6-1, securing her 28th victory on the WTA Tour and first since winning in Stuttgart in 2019.

The Czech was the Qatar Open runner-up last year to Aryna Sabalenka and champion over Muguruza in 2018, while she did not compete in 2019.

"It's been a great run in Doha," Kvitova said on court post-match.

"It's been a great whole week. I just feel like home a little bit. I love the court, I love everything and the people are really friendly as well."

Two-time Wimbledon champion Kvitova hit 11 winners and was dominant on her serve throughout.

After a strong opening set, Kvitova was broken by Muguruza early in the second but the Czech hit back by winning the next six games to secure the win, extending her head-to-head record over the Spaniard to 5-1.

Muguruza said: "Today I think Petra played very well from the baseline, and it was hard to try to make her move, or try to do much… It really wasn't my day."

Andrey Rublev continued his remarkable 2021 as he saw off Stefanos Tsitsipas in straight sets to reach the final of the Rotterdam Open.

Tsitsipas has himself enjoyed a fine start to the year, reaching the semis of the Australian Open, but it was Rublev who progressed to the final in more routine fashion than might have been expected.

He prevailed 6-3 7-6 (7-2), marking his 12th win from 13 matches this season.

The victory also extended his winning streak in ATP 500 matches to 19. Only Roger Federer (28) and Andy Murray (21) have produced longer such runs.

"[I play tennis] to play at the best level, to play at the best tournaments, to try to compete, then to go deep and to try to win them," Rublev said in an on-court interview. "A final is always special, so I am going to try to do my best tomorrow [Sunday]."

Rublev is likely to require his best given the form Marton Fucsovics, his opponent, is in.

Fucsovics came through qualifying to reach the main draw and delivered a superb performance to stun world number 26 Borna Coric 6-4 6-1.

The final will be the third of Fucsovics' career and his first since February 2019, when he lost to Rublev's Russian compatriot Daniil Medvedev at the Sofia Open.

Daniil Medvedev will climb to number two in the ATP rankings later this month, with his small step signalling that big change is afoot in the men's game.

The leading two positions have been occupied by a combination of the 'Big Four' ever since Rafael Nadal climbed above Lleyton Hewitt to take second place on the ladder on July 25, 2005.

Nadal, Federer, Novak Djokovic and Andy Murray have all had spells at number one in the years since then, and no other player has had a look-in on those leading two positions.

Within days, however, that is about to change, as the younger generation of players gains a first foothold in the top two.

The ATP, which runs the men's game, said on Saturday that 25-year-old Medvedev is certain to nudge up one place from his current position of world number three when the rankings, are published on March 15.

The Russian is currently on 9,735 points, 115 points behind Nadal, and he has a first-round bye at the Open 13 Marseille next week.

The ATP, tweeted: "With the release of next week's @atptour draws, @DaniilMedwed is confirmed to become World No. 2 in @FedEx ATP Rankings on 15 March. Medvedev will be the 1st player in the Top 2 since 25 July 2005 other than the Big 4 of @DjokerNole, @RafaelNadal, @rogerfederer and @andy_murray."

Medvedev, who won the ATP World Tour Finals title in November and reached the Australian Open final last month, missed an early chance this week to move ahead of Nadal when he lost in the first round of the Rotterdam Open.

Andrey Rublev was pushed hard by Jeremy Chardy on Friday but eventually secured his 18th successive ATP 500 win to set up a semi-final meeting with Stefanos Tsitsipas at the Rotterdam Open.

Chardy managed to save match points in the second set, as Rublev wobbled at the crucial moment, but the Russian got the job done 7-6 (7-2) 6-7 (2-7) 6-4.

The pair were on court for just under two hours and 40 minutes and racked up a considerable number of winners, with Rublev's 44 eight more than the Frenchman.

His 18-match winning streak in ATP 500 events has only been bettered on five previous occasions since 2009, all of which were achieved by Andy Murray, Rafael Nadal or Roger Federer, who holds the record of 28 successive victories.

If he is to get any closer to Federer's remarkable haul, Rublev will have to go beyond Tsitsipas, but Friday's match took plenty out of him.

"I will try to do as much as I can to be ready for [the semi-final]… Stefanos also had two tough matches [this week]," said Rublev.

"He had three sets [on Thursday] and today he had three sets. Now he has to play doubles. It is not easy."

As Rublev alluded to, Tsitsipas certainly did not have it all his own way against another Russian, Karen Khachanov, coming from a set down to win 4-6 6-3 7-5.

Tsitsipas also had to contend with being 3-1 down in the third set – but Rublev knows all about the Greek's ability to come back from the brink having lost to him in last year's ATP Finals despite having match point.

"He [Khachanov] was playing great tennis and I wasn't sure if I would be able to compete," Tsitsipas said after the contest.

"I had an amazing 5-0 lead in the second set and that brought a lot of confidence into my game. We had great rallies and the quality of tennis was excellent. You need to stay as calm as possible in three-setters. I have won a lot in the past and with experience, it gives me an idea of how to play in these tight moments."

Borna Coric and Marton Fucsovics will go head-to-head in the other semi-final.

Croatian Coric came through in straight sets against Kei Nishikori, though it was by no means a straightforward victory as he was pushed to tie-breaks in both sets, winning 7-6 (7-2) 7-6 (7-4).

Fucsovics saw off Tommy Paul 6-4 6-3 to reach the last four.