Jenson Brooksby enhanced his growing reputation and set up showdown with Diego Schwartzman in the European Open semi-finals.

The 20-year-old American, who took a set off Novak Djokovic and rattled the world number one at the US Open, is shaping up as potentially his country's biggest hope for the future in the men's game.

Californian Brooksby crushed Spain's world number 44 Alejandro Davidovich Fokina 7-5 6-0, and second seed Schwartzman awaits after the Argentinian took down another 20-year-old American, Brandon Nakashima, scoring a 6-4 6-2 quarter-final win.

Schwartzman is the man who ended Andy Murray's hopes at the tournament in Antwerp.

Brooksby, who had to win two qualifying matches to reach the main draw, said: "Tomorrow will be a great match. I'm really looking forward to it. I'll get some rest tonight and get ready to battle again tomorrow."

The other semi-final will see Italian top seed Jannik Sinner take on South African seventh seed Lloyd Harris following their respective straight-sets wins over Arthur Rinderknech and Marton Fucsovics.

There will be an all-Russian semi-final at the Kremlin Cup in Moscow, after Aslan Karatsev and Karen Khachanov won through to the final four.

Second seed Karatsev sank the hopes of Frenchman Gilles Simon, breaking serve five times on the way to a 6-4 6-3 win, while third-seeded Khachanov edged out Australian John Millman. A 7-5 7-6 (7-4) grind featured 19 aces by Khachanov, the 2018 Kremlin Cup champion, who saved four set points in the second set.

Marin Cilic thrashed Pedro Martinez 6-1 6-2 to set up a tussle with Ricardas Berankis, the Lithuanian ending Adrian Mannarino's run with a 6-2 7-6 (7-1) success. Frenchman Mannarino had stunned Russian top seed Andrey Rublev in the previous round.

Maria Sakkari admitted she got twitchy before finishing off Simona Halep to reach the Kremlin Cup semi-finals.

The Greek star is chasing what would be just her second career title at WTA level, but the limited silverware belies her growing reputation: Sakkari has shot up to a career-high seventh in the world rankings during her best season on tour.

Looking to finish with a flourish, both in Moscow and next month at the season-ending WTA Finals, Sakkari scored a 6-4 6-4 victory over former world number one Halep on Friday.

The victory sets up a last-four clash with Ekaterina Alexandrova, after the Russian impressed a home crowd by landing a 6-3 6-4 win against top seed Aryna Sabalenka.

Yet Sakkari was almost reeled in by Halep from the point of victory in the second set, being unable to finish off the match on her own serve after building a 5-1 lead. Halep twice broke back, before dropping her own serve.

"It was a very tough match today," Sakkari said in an on-court interview. "It was the first time I'd played Simona, but I knew what to expect: she makes a lot of balls, more than any other player. I had a tough moment in the second set when I was 5-1 up, but finally, I found a way. I got a little nervous, a little bit tired.

"The last couple of months have been tough, I've been travelling a lot so haven't recovered enough. I just tried harder in the last game and just went for it."

Alexandrova's shock win over Sabalenka gave her a sixth career victory over a top-10 player. Second seed Garbine Muguruza followed Sabalenka out of the tournament, walloped 6-1 6-1 by in-form Estonian Anett Kontaveit, who has won 19 of her last 21 matches on tour, including beating Sakkari in the Ostrava final last month.

Kontaveit's semi-final opponent at the WTA 500 event will be Marketa Vondrousova, who claimed a 6-4 6-2 win over Anastasia Pavlyuchenkova.

At the Tenerife Open, Italian Camila Giorgi is the only seeded survivor in the semi-finals. The Italian fourth seed saw off Arantxa Rus 6-1 6-1, with Frenchwoman Alize Cornet and American Ann Li also among Friday's winners at the WTA 250 tournament.

Andy Murray fumed at his own mentality and "poor" attitude after falling to a straight-sets defeat to Diego Schwartzman at the European Open.

Two days on from beating Frances Tiafoe in a three-set epic, Murray fell to a 6-4 7-6 (8-6) loss to the second-seeded Argentine in Antwerp.

The three-time grand slam winner, who in January 2019 underwent hip resurfacing surgery, was 4-1 up in the first set but was reeled back in and lost out in a hard-fought contest.

Following the defeat, a frustrated Murray said: "I didn't make as many good decisions as I would have liked in the second set dealing with adversity.

"Mentally I was poor, and my attitude was poor on the court."

Murray is still slated to play in Austria and Stockholm before the season is out, while he could also enter the Paris Masters either via a wildcard entry or going through the qualifiers.

"There'll be a decision on the final Paris wildcard on Monday, but I might even play the qualis there," Murray added. 

"Sport is a results business. Play well or poorly doesn't really matter if you lose matches. You need to be winning. 

"That's what I want in the last few tournaments. They are really strong tournaments and there are no guarantees the results will come, but I want to win more matches."

Andrey Rublev's hopes of retaining the Kremlin Cup on home soil in Moscow are over after he suffered a surprise defeat to Adrian Mannarino.

Mannarino ultimately came out on top 5-7 7-6 (7-4) 6-3 but he had to do it the hard way, coming back from match point down to set up a meeting with Ricardas Berankis, who lost only tree games in a 6-2 6-1 win over Federico Coria.

Rublev was never cruising, however, as Mannarino only just fell short in the first set and then took the second to a tiebreak, which he eventually won to turn the tide.

The 33-year-old, who lost to Rublev in the final two years ago, took things up a notch in the decider and did not face a single break point as he got the job done despite the home support.

"The crowd was cheering for Andrey but that is normal," he said after reaching the quarter-finals. "I was happy to play with such a nice atmosphere.

"We have been playing for a long time without fans, so it is nice to enjoy a stadium with crowds now."

Second-seed Aslan Karatsev is now the favourite in Moscow, and the Russian had few issues in a 6-4 6-3 defeat of Egor Gerasimov.

Karatsev will face Gilles Simon next following his 6-3 6-2 win over Mackenzie McDonald, while Pedro Martinez won 6-3 6-4 over Filip Krajinovic to book his passage.

At the European Open in Antwerp, Andy Murray's hopes of winning a first ATP Tour title in two years were ended by number two seed Diego Schwartzman.

The Argentinian trailed 4-1 in the first set but fought back to win 6-4 7-6 (8-6) in his first ever match against the Scot, whose last tour triumph was in Antwerp.

In his on-court interview, Schwartzman said: "It was a pleasure to play against Andy. We had not played before and he is coming back and every week he is playing better and moving better.

"I have a lot of respect because when I grew up playing tennis, I was watching Roger [Federer], Rafa [Nadal], Andy and Novak [Djokovic] and right now playing against him is a pleasure for me."

Seventh seed Lloyd Harris is also into the quarter-finals after a straightforward 6-2 6-3 victory over Jan-Lennard Struff in just 72 minutes, Marton Fucsovics came through 6-7 (5-7) 6-3 6-1 against Roberto Bautista Agut and Brandon Nakashima edged past Henri Laaksonen 7-6 (7-5) 6-7 (5-7) 6-3 to earn the right to face Schwartzman.

Maria Sakkari secured her place at this year's WTA Finals by progressing to the last eight of the Kremlin Cup in Moscow.

The third seed was on court for just 34 minutes on Thursday as last-16 opponent Anna Kalinskaya was forced to retire through injury at 6-2 1-0 down.

Sakkari has enjoyed a successful year on the WTA circuit, reaching grand slam semi-finals for the first time in her career at the French Open and US Open.

Through to the quarter-finals in the Russian capital, where she will play Simona Halep, the 26-year-old becomes the first Greek woman to qualify for the year-end WTA Finals in Mexico.

Eighth seed Halep beat Veronika Kudermetova 6-1 7-6 (7-4), while world number 35 Marketa Vondrousova also prevailed in straight sets against Ukrainian Lesia Tsurenko.

Elsewhere, Ostrava Open champion Anett Kontaveit is through to her eighth quarter-final of 2021 after defeating Andrea Petkovic 6-1 6-4.

Meanwhile, at the Tenerife Open, fourth seed Camila Giorgi enjoyed a commanding 6-1 6-2 victory over Montenegro's Danka Kovinic.

However, there was no joy for seventh seed Clara Tauson as the Danish teenager went down 7-6 (7-4) 2-6 6-4 against China's Saisai Zheng.

Daniil Medvedev says it is "logical" that the age of Rafael Nadal, Roger Federer and Novak Djokovic has made it easier to play against the 'Big Three' of men's tennis.

For so long, that triumvirate has dominated the ATP Tour, with Djokovic winning three of the four grand slams on offer in 2021 – denied only a clean sweep by Medvedev at the US Open.

Nadal has struggled with a foot injury for most of the year, though, a problem that saw him miss out on Wimbledon, the Tokyo Olympics and Flushing Meadows after losing to Djokovic in the French Open semi-finals.

Federer, similarly, has missed large parts of the 2021 term after requiring a third operation on his right knee in the space of 18 months.

Medvedev accepted Djokovic had proven "he can beat everyone" in another sensational season, but – while heaping praise on a golden generation of tennis – the Russian said it is natural that time has caught up with all three.

"It would be silly to deny it…[it's] logical," he told reporters about the prospect of younger players replacing the greats at the top of the men's game.

"It is something natural. It is not something that I decide. It is evidence. They get old and now it is easier to play against them."

Medvedev only dropped one set across the entire tournament en route to securing a maiden slam at the US Open.

However, Medvedev was reticent to say the shift in power has taken place.

"I do not dare to speak of a generational change in tennis," Medvedev said.

"It is the best generation in the history of tennis.

"Nobody can come close to the results they have achieved.

"We all want to defeat that troika. And they don't want to lose either."

Medvedev then focused on his own progress, having pulled out of the Kremlin Cup citing injury problems from an early exit in Indian Wells.

"I want to win more Grand Slams," he continued. "I also want to be number one and be at the top of tennis for many years. But you can't win every tournament, it's impossible."

Aryna Sabalenka edged past Ajla Tomljanovic in the Kremlin Cup to reach the quarter-finals in her first match since contracting COVID-19 after the US Open semi-finals. 

Top seed Sabalenka – appearing in Moscow for the first time – had not played since being downed by Leylah Fernandez, having tested positive for coronavirus on the eve of the Indian Wells Open. 

The Belarusian, who sits second in the world rankings, profited from a bye in the first round before battling past Tomljanovic 7-6 (7-2) 4-6 6-1 on Wednesday as she fired 10 aces but made 30 unforced errors. 

Sabalenka will now meet Ekaterina Alexandrova after the Russian cruised past Anhelina Kalinina 6-4 6-1, while Anastasia Pavlyuchenkova comfortably defeated Bernarda Pera 6-2 7-5. 

Number two seed Garbine Muguruza also reached her seventh quarter-final of the season as she defeated Tereza Martincova 6-4 4-6 6-3 in just under three hours in Moscow. 

Meanwhile, Elina Svitolina was shocked in the Tenerife Open as she was dumped out by Maria Camila Osorio Serrano, who succeeded 5-7 6-3 6-2 to claim her first top-10 victory. 

Svitolina was the favourite in Spain and comfortably took the first set on Tuesday. However, inadequate light stopped play and the 19-year-old Osorio responded emphatically the following day to secure a memorable triumph. 

Ann Li coasted past Varvara Gracheva 6-4 6-2 after Anna Karolina Schmiedlova had dispatched Jaqueline Cristian 6-2 7-5 in the opening match of the day. 

Xinyu Wang retired injured against Alize Cornet, who led 4-1 in the decisive set, while Donna Vekic and Irina-Camelia Begu's match was suspended for bad light with the Croatian leading by a set. 

Karen Khachanov revealed he felt the nerves of playing in front of a home crowd as he marked his return to Moscow with a comeback victory in the Kremlin Cup.

Handed a bye for the opening round, third seed Khachanov made home advantage count in his first match as the Russian defeated Australian world number 50 James Duckworth 3-6 6-3 6-1 to reach the quarter-finals on Wednesday.

Khachanov – Olympic Games silver medallist, who triumphed in Moscow three years ago – will face another Australian, John Millman after he defeated Illya Marchenko 6-1 5-7 6-4 at the ATP 250 tournament.

"It always feel great to be back in your hometown, in a tournament where everything started for me as a professional tennis player," world number 31 Khachanov said.

"[This is] where I won my first matches, I got my first points. Since then, it's always great to come back home to see a crowd, [get] home support. It's also little bit more nervous, of course. But I always enjoy playing at home."

Khachanov was joined in going through to the last eight by sixth seed Marin Cilic – a two-time Kremlin Cup champion who overcame Tommy Paul 7-5 6-3.

At the European Open in Antwerp, top seed Jannik Sinner downed fellow Italian youngster Lorenzo Musetti 7-5 6-2 in the duo's first meeting as professionals.

"We never practice together, so it was kind of a new match," Sinner said post-match.

"He's an incredible player. He's a very great talent, so I hope we will have a couple of more matches on the pro tour, and obviously I'm very happy about my level today."

Arthur Rinderknech upstaged eighth seed Dusan Lajovic 6-3 4-6 6-2 to set up a quarter-final tie with Sinner, who is in the hunt for a fourth title of the season and a place at next month's ATP Finals in Turin.

Another emerging talent, qualifier Jenson Brooksby, bettered US Open quarter-finalist Botic van de Zandschulp 6-2 6-0, with Alejandro Davidovich Fokina sending third seed Cristian Garin packing 4-6 6-3 6-3.

Australian Minister for Immigration Alex Hawke insists Novak Djokovic would need to be fully vaccinated against COVID-19 in order to enter the country and defend his Australian Open title.

The Serbian is the top-ranked player in the world and could move clear of Rafael Nadal and Roger Federer for grand slam titles if he can claim his 21st at Melbourne Park.

However, Hawke's comments regarding vaccination requirements cast doubts over Djokovic's participation, with the 34-year-old previously declining to reveal his vaccination status.

"You'll need to be double vaccinated to visit Australia," Hawke said to Australian Broadcasting Corporation radio. "That's a universal application, not just to tennis players. I mean that every visitor to Australia will need to be double vaccinated.

"I don't have a message to Novak. I have a message to everybody that wishes to visit Australia. He'll need to be double vaccinated."

With recent reports suggesting that over a third of professional players have yet to be fully vaccinated, a significant number could be denied the chance to play in the opening grand slam of 2022.

The men's ATP and women's WTA tours have attempted to encourage players with reservations to get the vaccine, and Tennis Australia explained that it was working with government authorities regarding conditions for the tournament.

"Our understanding is that the details around international visitors entering the country are yet to be decided and we hope to have more information soon," Tennis Australia said in a statement.

Australia's health minister Greg Hunt defended the ruling, explaining that the decision had been taken with the safety of the country's citizens in mind.

"The [rules] apply to everyone without fear or favour," Hunt said. "It doesn't matter whether you are number one in the world or you are anything else."

Djokovic, who withdrew from the Indian Wells Masters this month, has won nine of his majors at the Australian Open.

Andy Murray says he will never forget his memorable clash with Frances Tiafoe at the European Open in Antwerp.

The former world number one saved two match points in the first round match and eventually triumphed 7-6 (7-2) 6-7 (7-9) 7-6 (10-8) in three hours and 45 minutes.

Murray's victory in an epic clash was the longest three-set match of the 2021 ATP season.

The battle had so many twists and turns that Murray, a veteran of 897 matches on tour, ended up having a long debrief with Tiafoe in the locker room afterwards.

Murray revealed it was the first conversation of that nature he had been involved in for more than a decade.

Indeed, the Briton only remembered going back over a match with one of his opponents twice before.

"I spent probably 30 minutes in the locker room afterwards just chatting to Frances," Murray said. "I had a long chat with Frances afterwards so I'll probably remember that and then the embrace at the end. 

"I guess so much went into it that I don't remember loads of points in the match, but obviously the end was special. 

"I've never played a match like that on the tour really. In the locker room we had a much more in-depth chat about tennis - that was kind of rare I would say. 

"I think maybe twice I've had that conversation in the locker room.

"Once was with [Jurgen] Melzer at the US Open after I beat him in five sets [in 2008] and we chatted a bit about the match.

"And then once after playing Jarkko Nieminen [at Wimbledon in 2010] because we were waiting to speak to the Queen after we played." 

Murray faces a tough test in the last 16 as he is due to do battle with second seed Diego Schwartzman.

He hit 21 aces against Tiafoe and totalled 46 winners to just 21 unforced errors, but Tiafoe was also in form with 51 winners to 25 unforced errors.

"The margins were so fine," added Murray. "I served particularly well at the end, which helped, and when he missed his first serve on that match point I was able to capitalise on that.

"There's obviously so much that goes into a match like that."

Schwartzman will go into the next match fresher than Murray as the Argentine received a first-round bye due to his seeding.

Andy Murray saved two match points before winning an epic encounter with Frances Tiafoe at the European Open in Antwerp.

The former world number one emerged triumphant from a gruelling contest lasting three hours and 45 minutes, the longest three-set match of the 2021 ATP season.

Having warded off two match points in the decisive tie-break, Murray clinched a 7-6 (7-2) 6-7 (7-9) 7-6 (10-8) victory with a drop shot that landed just out of Tiafoe's reach.

"I think that's the first time in my career I've played a 7-6, 6-7, 7-6 [match]. I don't think I've ever played a match like that," said Murray, who next faces second seed Diego Schwartzman. "I think it's the longest three-set match I've played by quite a distance. I'm tired right now, obviously it was an unbelievable battle.

"Nowadays obviously my body is old now. I've played a lot of matches on the tour. I don't mind playing long matches, but that was taking it to another level.

"Brilliant match, amazing atmosphere, thanks to everyone who came and supported. It's just so nice to be back and playing in front of crowds again."

American prospect Jenson Brooksby left his compatriot Reilly Opelka flummoxed as the fifth seed was beaten 6-4 6-4.

Opelka was heard proclaiming Brooksby was the "best player I've played in my whole life" during the second set as he struggled to interpret the 20-year-old's service game. Brooksby will face Botic van de Zandschulp in the next round.

There was another upset when sixth seed Alex de Minaur lost 6-4 6-0 to Brandon Nakashima, who has twice reached ATP-level finals this year and will next face Henri Laaksonen, victorious over Benoit Paire.

Lorenzo Musetti needed two tie-breaks to defeat fellow Italian Gianluca Mager, while Alejandro Davidovich Fokina – quarter-finalist at the French Open this year – eased past Jordan Thompson 6-3 6-3.

At the Kremlin Cup, fifth seed Alexander Bublik suffered a surprise straight-sets defeat to Illya Marchenko, the world number 164 winning by a 6-4 6-3 scoreline.

Adrian Mannarino battled through against wildcard Roman Safiullin, but Laslo Djere lost in three sets to Gilles Simon.

Ricardas Berankis and Egor Gerasimov also progressed, while Guido Pella retired from his match with Pedro Martinez.

Simona Halep reached the second round of the Kremlin Cup on Tuesday with a straight-sets win over home hope Anastasia Potapova.

The former world number one, competing at the Moscow event for the first time since 2013, won 6-1 6-4 to set up a meeting with Veronika Kudermetova, who survived a marathon contest with qualifier Oksana Selekhmeteva.

Anett Kontaveit, who won the title in Ostrava last month, prevailed 6-3 6-3 against Katerina Siniakova. Another seed, Wimbledon quarter-finalist Ons Jabeur, retired against Ekaterina Alexandrova when trailing 6-1 1-0.

Andrea Petkovic also progressed when Jelena Ostapenko had to halt proceedings in their third set, while seventh seed Elena Rybakina lost in straight sets to Olympic silver medallist Marketa Vondrousova.

At the Tenerife Open, Camila Giorgi progressed past Aliona Bolsova 7-6 (7-4) 3-6 6-4 despite giving up two penalty games due to repeated indiscretions when line calls were called into question.

Fifth seed Viktorija Golubic lost in straight sets to Arantxa Rus, while Alison Riske was dispatched 6-1 6-4 by Donna Vekic.

Seventh seed Clara Tauson defeated Heather Watson via a final-set tie-break, while Varvara Gracheva won in the same vein against third seed Sara Sorribes Tormo in a match lasting nearly three and a half hours.

Top seed Elina Svitolina was one set up against Maria Camila Osorio Serrano when their match was suspended for the night.

World number one Novak Djokovic is unsure if he will defend his Australian Open crown in Melbourne next year due to vaccination requirements.

The state of Victoria, where the year's opening grand slam takes place at Melbourne Park, has introduced a vaccine mandate for professional athletes and across most industries amid the coronavirus pandemic.

The 2021 Australian Open went ahead, albeit in February instead of January, and without fans for most of the tournament following a snap lockdown of Melbourne due to COVID-19.

Djokovic was among the players critical of the conditions athletes endured prior to this year's Australian Open, with strict quarantine measures introduced, though the nine-time champion cast doubt over his participation.

"Things being as they are, I still don't know if I will go to Melbourne," 20-time major winner Djokovic told Blic. "I will not reveal my status whether I have been vaccinated or not, it is a private matter and an inappropriate inquiry.

"People go too far these days in taking the liberty to ask questions and judge a person. Whatever you say 'yes, no, maybe, I am thinking about it', they will take advantage."

"Of course I want to go, Australia is my most successful grand slam tournament. I want to compete. I love this sport and I am still motivated," said Djokovic, who has not played since losing in the US Open final, having withdrew from the Indian Wells Masters.

"I am following the situation regarding the Australian Open and I understand the final decision [on COVID-related restrictions] will be made in two weeks. I believe there will be a lot of restrictions just like this year, but I doubt there will be too many changes.

"My manager, who is in contact with the Australian Tennis Federation, tells me they are trying to improve the conditions for everyone, both for those who have been vaccinated and those who have not."

Victoria state premier Daniel Andrews responded to Djokovic's comments on Tuesday, saying it was unlikely unvaccinated players would be granted a visa to travel to Australia.

"I don't think an unvaccinated tennis player is going to get a visa to come into this country and if they did get a visa they'd probably have to quarantine for a couple of weeks," Andrews told reporters.

Arthur Rinderknech continued his fantastic season by defeating Federico Delbonis at the European Open, while Marin Cilic battled through in the Kremlin Cup.

Rinderknech, who sits 65th in the world rankings, had not recorded a Tour-level victory before 2021 but has now triumphed 15 times after cruising past Delbonis 6-4 6-4.

The Frenchman will meet eighth seed Dusan Lajovic in the second round in Antwerp, after the Serbian downed Richard Gasquet 7-6 (7-3) 6-1 on Monday.

The other first-round clash in Belgium saw Alexei Popyrin capitulate in the third set as he succumbed to a 4-6 6-3 0-6 defeat against world number 62 Botic van de Zandschulp.

Americans Jenson Brooksby and Brandon Nakashima also booked their places in the main draw. Brooksby defeated Norbert Gombos 6-4 6-2, while Nakashima overcame Pierre-Hugues Herbert 6-2 6-4.

Meanwhile in Russia, Cilic – who has claimed the crown in Moscow twice previously – recovered from a first-set scare in his round-of-32 tie with qualifier Damir Dzumhur, eventually triumphing 6-7 (4-7) 6-1 6-1.

John Millman experienced similar difficulties, with Benjamin Bonzi claiming the first set before the Australian succeeded 6-7 (5-7) 6-4 6-3 to set up a potential second-round match against fifth seed Alexander Bublik.

Daria Kasatkina suffered a first-round defeat against Anhelina Kalinina in the Kremlin Cup, while Jaqueline Cristian stunned Tamara Zidansek at the Tenerife Open.

World number 28 Kasatkina, who has won four WTA Tour titles, fell on home soil to Kalinina as the Ukrainian triumphed 6-2 6-3 on Monday.

Ajla Tomljanovic cruised past Liudmilla Samsonova in similar fashion, claiming a 6-2 6-4 victory in Moscow to set up a last-16 clash with top seed Aryna Sabalenka, who is ranked second in the world.

Anna Kalinskaya joins Tomljanovic in the next round as she defeated Dayana Yastremska 7-6 (7-5) 6-4 on home soil and the Russian will now face French and US Open semi-finalist Maria Sakkari.

Lesia Tsurenko had no issues against China's Qinwen Zheng as she won 6-4 6-3, while American Bernarda Pera beat Aleksandra Krunic 7-6 (7-3) 6-3 to seal her second-round berth.

Meanwhile, number two seed Zidansek, who sits 33rd in the world rankings, crashed out in Tenerife as world number 108 Jaqueline Cristian succeeded 7-5 4-6 6-1.

Zhang Shuai was the sixth favourite in Spain but she lost to fellow Chinese star Wang Xinyu 6-2 6-1, with Anna Karolina Schmiedlova also defeating Kaja Juvan 4-6 6-1 6-4 and Irina-Camelia Begu overcoming Marta Kostyuk 6-4 6-4.