Novak Djokovic may have missed out on completing a Grand Slam in 2021 but his "crazy" achievements across the year have received praise from Roger Federer. 

Djokovic fell at the final hurdle in his bid to secure a clean sweep of the majors, losing in straight sets to Daniil Medvedev at the US Open.

The Serbian's defeat at Flushing Meadows means Rod Laver remains the last man to claim all four majors in one year, the Australian doing so for a second time in 1969 having previously managed the feat seven years earlier. 

Neither Federer, who missed out on playing in New York due to knee surgery, nor Rafael Nadal have done so in their stellar careers, though the Swiss is certain a calendar slam is still possible.

"Will it actually happen again, that a player will win all four grand slams in their career? I think so," Federer said.

"We have seen with Rafael Nadal, Novak Djokovic and of course with me as well that this is possible.  

"It is extremely hard, of course. But I have the feeling, more than ever, that we can dominate on all kinds of ground where we have all found our own game.  

"The problem is mentally and physically it is not getting any easier for any of us. So, what Novak was able to accomplish this year has to be highly rated. It was absolute top class. It was crazy." 

Federer confirmed he would be out for "many months" when revealing he would require a third procedure on his problematic right knee in the space of 18 months.

However, the 40-year-old – who sits tied with long-time rivals Djokovic and Nadal on 20 grand slam singles titles – has suffered no setbacks in his recovery so far, putting him on course for a competitive return to the ATP Tour in the 2022 season.

"I'm feeling actually really good, considering, you know, that things are not as I hoped they would be, but I'm recovering well and the rehab is going really good, I must say," Federer said. 

"I've had no setbacks. You know, every day is a better day. I'm feeling strong and excited for what's to come."

Federer has not played since losing in straight sets to Hubert Hurkacz in the Wimbledon quarter-finals back in July.

Lorenzo Sonego made an impressive start at the Moselle Open as the fifth seed defeated Marton Fucsovics in straight sets. 

The Italian recorded his 25th win of the year on the ATP Tour on Monday, winning 6-3 6-2 in 73 minutes while not even conceding a break point to Fucsovics. 

"I was really focused," said Sonego. "Marton is a great player and it was a tough match. I liked my tennis and I am really happy.  

"I am confident because this year has been my best. I am now number 24 in the world, which is my best ranking. I have played my best tennis this year." 

Vasek Pospisil also moved through, beating home wildcard hope Gregoire Barrere 6-3 6-4. 

Hubert Hurkacz is the top seed at the ATP 250 event in Metz, with Gael Monfils and Andy Murray among the other stars yet to play their first match. 

At the Astana Open, which has the same ranking points available, Miomir Kecmanovic was a 6-4 6-2 winner over Fernando Verdasco. 

Seventh seed Laslo Djere, meanwhile, had to battle hard to end a four-match losing streak on the ATP Tour. He edged into the last 16 with a gruelling 6-4 3-6 6-4 win over Colombia's Daniel Elahi Galan. 

The highest-ranked players in the tournament are Russian Aslan Karatsev and home hope Alexander Bublik. 

Second seed Bublik will start his campaign against Kecmanovic, whose victory over Verdasco was his first win since the Tokyo Olympics in July. 

Paula Badosa got her campaign off to a winning start as the Ostrava Open began on Monday. 

Iga Swiatek, Petra Kvitova, Belinda Bencic and Maria Sakkari are among the top names at the WTA 500 event, though they are all yet to begin their campaigns. 

World number 27 Badosa was the only seed in action, and she started her week in smooth fashion with a 6-2 6-2 triumph over Russian qualifier Varvara Gracheva. 

In a dominant performance, Badosa did not even concede a break point as she triumphed in 73 minutes to gain some revenge for her defeat to Gracheva at the US Open earlier this month. 

Fellow Spaniard Sara Sorribes Tormo joined Badosa in claiming a first-round victory, though she had to work much harder to see off Anastasia Zakharova. 

While Sorribes Tormo triumphed 6-3 6-3, she was given a stern examination by Zakharova, who forced nine break points in the contest but paid the price for converting just two. 

The prize for Sorribes Tormos is a testing last-16 tie against Olympic gold medallist Bencic. 

Caroline Garcia, meanwhile, was a day one casualty as she lost in straight sets to Anastasia Potapova. 

Potapova will now take on two-time Wimbledon champion Kvitova, who will be playing in front of her home fans in the Czech Republic. 

Stefanos Tsitsipas plans to get the COVID-19 vaccine, having previously declared he would only do so if the ATP Tour made it mandatory.

Greek world number three Tsitsipas revealed last month he would not get a jab due to concerns over side effects.

The ATP Tour has persisted in encouraging players to get vaccinated, with Novak Djokovic the most high profile to have stated he was opposed to it, and Tsitsipas has now backtracked on his original stance.

"I will get vaccinated this year," the 23-year-old told Greek outlet Antenna TV. "So I can go to restaurants and shops. I support all those who get vaccinated.

"I am not a doctor; I am a tennis player, so I may not have the most substantiated opinion when it comes to medical issues."

The French Open runner-up was subject to backlash in his homeland following his initial comments on the vaccine, with a series of top figures questioning his thought process.

"The COVID-19 vaccine has not been tested enough because it is new and has some side effects," said Tsitsipas.

"I know some people who've had them. I'm not against it, I just see no reason for someone in my age group to be vaccinated [yet].

"For us young people I think it's good to pass the virus because we'll build immunity.

"I don't see it as something bad. As I said, it isn't obligatory, everyone has freedom to decide for themselves what's right and what's not. At some point we should all do it, I'm not saying the opposite.

"The time will come when we will not be given many options, but until then I want to see a better version of the vaccine that gives us more pluses than minuses."

Tsitsipas is set to play for Team Europe at the Laver Cup this week after missing Greece's Davis Cup tie with Lithuania due to a foot injury.

Jasmine Paolini battled to a straight-sets victory over Alison Riske in Sunday's Portoroz final to win her maiden WTA singles title.

World number 87 Paolini had already eliminated three seeded players to reach her first final and she recovered from a slow start to see off another 7-6 (7-4) 6-2.

Third seed Riske led 5-2 in the first set after breaking her opponent's serve three times in the opening seven games, but Paolini dug deep and took four games on the spin.

The Italian used that momentum in the tie-break to open up a 5-2 advantage before getting over the line with her second set point.

After a gruelling 63-minute opening set, Paolini found the second a more straightforward affair as she broke for 3-2 and reeled off the remaining games, the last of those points coming via an error-forcing forehand.

Paolini, who won two-thirds of her second-service points and converted six of her 10 break points, is glad her hard work has paid off with a first singles success at the age of 25.

"It's been an amazing week here in Portoroz," she said in her on-court interview. "I feel just very happy, it's a big achievement for me, to win my first title. It's special to do it on the hard court.

"It wasn't easy to go through to the final. I'm proud of myself because I never gave up.

"I'm working really hard in the past couple of months. I understood more about my game, I think. I just want to keep this level for all the season that is almost finished, and to stay strong and keep this level."

Danish teenager Clara Tauson set up a Luxembourg Open final showdown with Jelena Ostapenko, showing off the prowess that saw her beat Emma Raducanu in Chicago prior to the US Open.

Raducanu recovered from that setback in the final of August's Challenger tournament in the Windy City, charging to a shock Flushing Meadows triumph, but fellow 18-year-old Tauson awaits her big breakthrough at the majors.

Tauson took down a former French Open runner-up and current Olympic silver medallist in reaching the Luxembourg final, beating Marketa Vondrousova in three sets, and now must overcome a player who has been champion at Roland Garros in Ostapenko.

She prised the vital break of serve in the ninth game of the decider against Vondrousova, upping the power in her shots, before serving out for a 6-4 2-6 6-4 victory.

Tauson will be going for a second title of the year, having won the Lyon Open in March.

Defending champion Ostapenko raced to a 6-1 5-1 lead over Liudmila Samsonova but then began to misfire and had to scramble from the brink of being taken to a third set.

Ostapenko eventually prevailed 6-1 7-6 (7-4), having trailed 4-1 in the tie-break, and she will attempt to scoop a fifth WTA title on Sunday. Her most recent came at Eastbourne in the week before Wimbledon.

At the WTA tournament in the Slovenian town of Portoroz, Sunday's final will feature American Alison Riske and Italy's Jasmine Paolini.

Riske denied Slovenian Kaja Juvan a place in a home final, earning a 6-0 6-4 win in their semi-final, while Paolini sprang a shock by beating Kazakhstan's Yulia Putintseva 1-6 6-3 6-4.

Belinda Bencic made a winning return to action as the Olympic champion defeated Zarina Diyas to seal a quarter-final spot at the Luxembourg Open.

Bencic, the unlikely successor in Tokyo, triumphed in straight sets 6-1 6-3 on Thursday to tee up a last-eight encounter with Liudmila Samsonova, who the Swiss lost to in Berlin earlier this year.

It was a welcome return to form for world number 12 Bencic after her defeat to eventual champion Emma Raducanu in the US Open quarter-finals last week.

Joining the top seed in the quarters is defending Luxembourg Open champion Jelena Ostapenko, who needed three sets to overcome Arianne Hartono.

Second seed Elise Mertens also progressed, though she had to come from behind to beat Aliaksandra Sasnovich 3-6 6-2 7-5.

In Thursday's other last-16 tie, Marie Bouzkova beat Greet Minnen to round off the quarter-finals line up.

Meanwhile, Sorana Cirstea and Jasmine Paolini will meet in the Zavarovalnica Sava Portoroz quarter-finals after respective victories over Tereza Martincova and Anna Kalinskaya.

There was a sense of deja vu as Clara Tauson upset fourth seed Ekaterina Alexandrova at the Luxembourg Open.

The 18-year-old defeated the same opponent en route to claiming a maiden WTA Tour title in Lyon in March and repeated the feat here, again on an indoor court.

On this occasion, Tauson needed to come back from a break down in the deciding set to clinch a 6-4 3-6 7-6 (7-1) triumph and book her spot in the quarter-finals.

Fifth seed Marketa Vondrousova had no such trouble, the Czech a comfortable 6-2 6-4 victor over Jana Fett. Alize Cornet (8) also made the last eight with a 6-3 6-3 win over Mandy Minella, while Ludmilla Samsonova (7) needed a pair of tie-breaks to overcome Oceane Dodin.

In the first round, Zhang Shuai (6) lost in three sets to Marie Bouzkova.

At the Zavarovalnica Sava Portoroz in Slovenia, second seed Yulia Putintseva was a 6-3 6-1 winner over Katie Boulter. Alison Riske, Kristina Mladenovic and Lucia Bronzetti also made it through.

Emma Raducanu still has the hunger to continue improving following her record-breaking US Open triumph and is targeting a possible return to action at Indian Wells.

The 18-year-old became the first qualifier in history to win a grand slam when defeating Leylah Fernandez ​in straight sets in Saturday's final at Flushing Meadows.

Raducanu, ranked 150 by the WTA before beginning her three-week long tournament, did not drop a single set across her 10 matches.

That victory in New York capped a life-changing couple of months for Raducanu, who also reached the last 16 of Wimbledon in her only other grand slam appearance before withdrawing due to medical reasons.

After spending a few days away from the court and taking in some of the sights the Big Apple has to offer, the Briton is ready to start preparing for her next tournament.

"I have a few days' rest and recovery," Raducanu, who became the first British female to win a major tournament since Virginia Wade on home soil at Wimbledon 44 years ago, told CNBC's Closing Bell programme.

"I think it was needed after the last seven weeks but then I am straight back to training and hungry to get better and come back out and play some more tournaments."

Raducanu was originally due to take part in qualifying for the Chicago Fall Tennis Classic later this month, but she may instead wait for next month's delayed Paribas Open in Indian Wells, where a wildcard entry is likely.

"After the US Open I wanted to give myself this week to completely switch off from tennis because it's been an extremely intense but rewarding seven weeks," she told the WTA's official website. 

"But I've worked very hard to finish on such a high with the US Open, a whole week off was needed.

"I know I'll get back to work probably Monday or early next week to get back to training again. Schedule-wise, I'm not sure. Maybe Indian Wells, I don't know. I'm going back to London before my next tournament for sure."

Defending champion Jelena Ostapenko booked her place in the last 16 of the Luxembourg Open with a comfortable straight-sets win over Jule Niemeier.

The world number 30 came out on top 6-2 6-2 in a little under an hour to set up a meeting with Arianne Hartono, who earlier beat Anna-Lena Friedsam 7-6 (7-5) 3-6 7-6 (7-4).

Fifth seed Marketa Vondrousova also shuffled through to the next round thanks to a 6-2 6-3 triumph against Alison Van Uytvanck, while Zarina Diyas will face tournament favourite and Olympic champion Belinda Bencic next after beating Anna Karolina Schmiedlova in three sets.

Aliaksandra Sasnovich was made to work harder for her 7-5 7-6 (8-6) win against Lesia Tsurenko, with that the longest straight-sets match of 2021 so far at two hours and 30 minutes, according to the WTA.

Greet Minnen and Mandy Minella were also victorious on Tuesday, overcoming Nuria Parrizas-Diaz and Varvara Gracheva respectively.

At Zavarovalnica Sava Portoroz in Slovenia, meanwhile, home favourite Kaja Juvan eliminated top seed Petra Martic with a 6-3 6-4 win. Sweden's Rebecca Peterson was another seed to fall, going down in straight sets to Lucia Bronzetti.

Novak Djokovic was "playing for history" and suffered from nerves in his US Open final defeat to Daniil Medvedev, according to previous champion Dominic Thiem, who backed the 34-year-old to return "stronger than ever" in 2022.

Medvedev prevented Djokovic from becoming the first man since Rod Laver in 1969 to win all four grand slams in a single year, beating him 6-4 6-4 6-4 in Sunday's thrilling showpiece.

Djokovic was seen in tears during the third set as his hopes of adding the US Open to his run of wins at the Australian Open, French Open and Wimbledon this year slipped away.

But Thiem tipped Djokovic to bounce back from the disappointment of defeat and return in 2022 even stronger.

"One unbelievable goal slipped out of his hands yesterday," Thiem told Stats Perform.

"I expect him to be as strong as ever in 2022. I think after he won in Roland Garros, everybody was only talking about the calendar slam – first about the golden slam, and then about the calendar slam.

"He [Djokovic] was under pressure. Nobody can feel that or anything like that because of it being the calendar slam.

"I can feel it in a smaller way, probably from last year's final and from some other matches. And at some points it's just getting to you. And so, I really felt for him as well towards the end of the match.

"So, it can happen that it also makes him even stronger next year when all these talks and all this pressure is not that big anymore."

Thiem, who missed the tournament with a wrist injury that will rule him out until 2022, believes nerves were a factor in Djokovic's defeat but agreed with Medvedev's assessment of the Serbian as the greatest of all time – though he could not set him apart from Roger Federer and Rafael Nadal.

"For me, there are three GOATs in the game, and each of them has achieved something very unique," Thiem said of the trio locked on 20 major titles each.

"So it's still the same for me as it was before. The three of them are the best in the history to me.

"And I'm only super happy to be in the same era with them and to be able to compete with them. Hopefully many more times next year again."

Dominic Thiem believes Emma Raducanu's sensational US Open triumph might be the "greatest breakthrough performance of all time".

Raducanu, 18, overcame fellow teenager Leylah Fernandez 6-4 6-3 on Saturday to cement her place in history.

Her triumph meant she became the first qualifier – male or female – in tennis history to win a grand slam final.

She did not lose a set in 10 matches across qualifying and the main draw, becoming the first player since Serena Williams in 2014 to win the US Open without dropping a single set.

Raducanu – whose first grand slam appearance only came at Wimbledon in June – was ranked 150th in the world before the US Open, but her stunning win in New York has seen her break into the top 30.

Thiem, who missed the men's tournament with a wrist injury, was in awe of Raducanu's stunning run at Flushing Meadows and says he can scarcely recall a more impressive breakthrough in the sport.  

"There were some other great achievements in the past but with Emma Raducanu, starting in the qualifiers and then playing such great tennis and making this incredible path, it's definitely, maybe, the greatest breakthrough performance of all time," he exclusively told Stats Perform.

"It's an incredible journey if you look at the stats. She didn't lose one set the whole tournament. She came from qualifying and she didn't even play one tie-break. That's simply amazing and something that was probably never witnessed before.

"And also the way she plays, her technique, the way she moves, somehow she brought it up to a new level for the whole game and it was great to see.

"But as well, her opponent, it was so fun to watch her. I was excited for it, watching every single point on TV. And it was great not only for women's tennis, but for all sports in general."

Fourth seed Ekaterina Alexandrova needed three sets to edge past Stefanie Vogele in the round of 32 at the Luxembourg Open.

Russian Alexandrova was pushed to three sets by her Swiss opponent but ultimately outclassed Vogele to prevail 6-1 3-6 6-3 to book her place in the last 16.

She is joined there by compatriot Liudmila Samsonova, who overcame Misaki Doi 6-2 6-3, and eighth seed Alize Cornet, who beat Anastasia Potapova 6-4 6-2.

There were also wins for Clara Tauson, Jana Fett and Oceane Dodin.

At Zavarovalnica Sava Portoroz in Slovenia, meanwhile, there were victories for Viktoria Kuzmova, Sorana Cirstea and Lucia Bronzetti.

Shock US Open champion Emma Raducanu has what it takes to win Wimbledon in the future, according to British great Virginia Wade.

Raducanu, 18, beat fellow debutant finalist Leylah Fernandez 6-4 6-3 on Saturday to become the first qualifier – male or female – in tennis history to win a grand slam final.

The British sensation – the youngest women's grand slam finalist since a 17-year-old Maria Sharapova took the title at Wimbledon in 2004 – did not lose a set in 10 matches across qualifying and the main draw, becoming the first player since Serena Williams in 2014 to win the US Open without dropping a single set.

The triumph also saw her become the first British woman to win a major tournament since Wade claimed the Wimbledon crown 44 years ago.

Raducanu reached the last 16 of this year's Wimbledon – her only other grand slam appearance – before pulling out of the competition due to medical reasons.

Wade, who was in attendance for the final at Arthur Ashe Stadium, believes Raducanu has all the attributes to follow in her footsteps and win British tennis' showpiece tournament during what she predicts will be a glittering career.

"I see her winning Wimbledon some time," Wade exclusively told Stats Perform. "I don't have a crystal ball, so I don't know when.

"I feel sure her time will come. She's just too good not to.

"Physically she's wonderful, she's the right height, has long legs, moves smoothly and is very quick from left to right.

"She's light on her feet, reads the ball well, her serve is terrific and her groundstrokes are solid.

"She's got balance out there and her concentration and determination are important factors as well."

Fernandez, 19, defeated top five trio Naomi Osaka, Elina Svitolina and Aryna Sabalenka along with three-time major winner Angelique Kerber on her way to Saturday's final.

And although she succumbed to a straight sets defeat, Wade believes the Canadian, along with Raducanu, will dominate the women's game for years to come.

"They're both absolutely terrific players and they enchanted everybody," she added. "Everybody was thrilled with them.

"You only get these extra special players once in a decade or once every two decades.

"In the women's game we have a really solid block of really good players. In my mind there are six to 10 players who will have to share the hardware in the next five to 10 years because they are all good. It's impossible for someone to win them all.

"Emma and Leylah will have their fair share of winning, and probably more than the others, being at the top and being feared."

Daniil Medvedev was relieved to close out his first grand slam title at the US Open after revealing he was cramping in his quest to conquer Novak Djokovic.

Medvedev blitzed world number one and 20-time major champion Djokovic 6-4 6-4 6-4 in the men's final at Flushing Meadows on Sunday.

Djokovic's bid to become just the third man and first since Rod Laver in 1969 to claim a calendar Grand Slam, and to surpass Roger Federer and Rafael Nadal for the most major men's titles, was emphatically ended by Medvedev.

Medvedev fired down 16 aces and hit 38 winners in a ruthless display on Arthur Ashe Stadium. However, the second seed conceded he was worried at the end of the third set as he tried to see off Djokovic.

Russian star Medvedev double-faulted twice in succession when his first championship point arrived and gave back one of those breaks to Djokovic, who closed to 5-4. But the former came out to serve again and again served a double on a championship point, though he had another in store and the Serb netted on the backhand.

"I definitely had it [pressure]," Medvedev – who lost to Djokovic in the 2021 Australian Open final, having gone down to Nadal in the 2019 US Open showpiece – told reporters. "I started cramping at 5-3, I think because of the pressure at 5-2 where I had match points, I didn't make it. My legs were gone after 5-3. At 5-4, left leg, I almost couldn't walk. If you really look the replay, when I walked to the towel, my leg was just going behind. I was trying not to show it. If Novak feels it, it's not good.

"Again, 40-15, that's two match points. I was like, C'mon, go for an ace, just try to make it. I had a huge double-fault. Second one was like in the middle of the net. Okay, I have one more. Just try to make a first serve. I made it and I'm really happy."

Medvedev became the first Russian man to win a grand slam since Marat Safin at the 2005 Australian Open.

The 25-year-old also became the ninth different men's champion of the last 14 years in New York, including first-time major winners Dominic Thiem, Marin Cilic, Andy Murray and Juan Martin del Potro. During the same time, the Australian Open, French Open and Wimbledon have each been claimed by four different men.

Medvedev – the second player since Ivan Lendl in 1987 to lose just one set en route to the men's US Open crown after Nadal in 2010 – is the fifth player to clinch a slam final against Djokovic.

He is also the fourth player with four or more wins over Djokovic as world number one, after Nadal (nine), Federer (five) and Murray (five).

"It definitely makes it sweeter [beating a world number one for first major trophy]," Medvedev said. "I mean, a grand slam is a grand slam. I would win it against Botic [Van de Zandschulp] in the final, probably I would be same happy.

"For the confidence and for my future career, knowing that I beat somebody who was 27-0 in a year in grand slams, I lost to him in Australia, he was going for huge history, and knowing that I managed to stop him it definitely makes it sweeter and brings me confidence for what is to come on hard courts so far, but let's see about other surfaces."

Medvedev was also asked about his celebration – the 13-time ATP Tour champion fell to the court after vanquishing Djokovic, with his eyes closed and tongue out.

It was in reference to FIFA's video game and the "dead fish" celebration.

"I like to play FIFA," he said. "I like to play PlayStation. It's called the dead fish celebration. If you know your opponent when you play FIFA, many times you're going to do this. You're going to score a goal, you're up 5-0, you do this one.

"I talked to the guys in the locker, they're young guys, super chill guys. They play FIFA. They were like, That's legendary. Everybody who I saw who plays FIFA thinks that's legendary. That's how I wanted to make it.

"Again, it's not because I want to be on the newspaper talking about FIFA celebration or whatever. I don't care. But I wanted to make it special for people to love, for my friends to love who I play FIFA with. I knew I'm going to make it. I got hurt a little bit. It's not easy to make it on hard courts. I got hurt a little bit, but I'm happy I made it legendary for myself."