The winner moves onto the semi-finals at The O2; the loser's debut at the Nitto ATP Finals comes to an end.

Roger Federer has clinched the top spot in the group by beating both Zverev and Sock. But since both season finale debutants defeated Marin Cilic to claim 1-1 records, the winner between the two will finish second and earn a spot in the final four in London.

So while Zverev was disappointed to lose a tough three-setter against Federer on Tuesday in which he looked at least the equal of the Swiss for the first two sets, he is not down on himself. How does he feel?

“Good, because I still have a very decent chance of being in the semi-finals,” Zverev said. “It was a pretty positive match. I think we both played pretty well. I feel very confident going into the Sock match.”

The 20-year-old German is not the only one who will take the court with confidence. Sock is still playing with house money after soaring up the Emirates ATP Race To London in its final week, moving from No. 24 into the season finale cut with his first ATP World Tour Masters 1000 title at the Rolex Paris Masters. Much like in Paris, Sock wasn’t sure about the qualification scenarios after his victory against Cilic on Tuesday, but he is not looking ahead to the semi-finals.

“There's still a long way to go for that,” Sock said. “I'm just focused on my tennis. I obviously know I have to win...I knew if I did the right things, played some good tennis, I could give myself a chance. That's kind of what I'm here to do.”

And with one clash standing between either Zverev or Sock and the semi-finals, anything can happen. The pair’s FedEx ATP Head2Head rivalry is knotted at 1-1, with both matches coming last year on hard courts. Sock won a two-hour, 48-minute battle in their only indoor hard court match, which came in Stockholm.

The major difference between the two matches was Sock’s performance on his second serve. The American won just 43 per cent of second-serve points in their first meeting in Beijing last year, before upping that number to 62 per cent in Sweden just weeks later.

But both players have come a long way since then. Each has broken into the Top 10 of the Emirates ATP Rankings, with Zverev rising all the way from No. 20 the week of his loss against Sock in Stockholm to where he is now: third in the world. Sock, who was 23rd in the rankings at the time, is now up to ninth.

For the second match in a row, Sock’s lethal topspin forehand will likely end up in rallies against an excellent backhand in Zverev’s two-hander. Court positioning will also be key, as even with a tremendous forehand, it will be tough for Sock to control points if the German is closer to the baseline and the player stepping into his shots, as he tends to be.

Last year, Jamie Murray and Bruno Soares were perfect in group play at the Nitto ATP Finals before falling in the semi-finals. But after losing a tough opener this season, they were in jeopardy of not making the semi-finals at all.

The Scottish-Brazilian kept their hopes alive on Wednesday with an impressive 6-1, 6-1 victory against Ivan Dodig and Marcel Granollers in 52 minutes.

"Now it's a normal tournament. If we win, we keep going forward. If we lose, we're on holidays," Murray said. "We played a great match. We've got a good chance on Friday to progress further in the tournament.

It may have been the first meeting between the two teams, but Murray and Soares certainly made a strong first impression, eliminating Dodig and Granollers from semi-final contention.

Murray was flying around the net in the early exchanges, poaching with swinging forehand volleys, while Soares put on a masterclass from the baseline, working his own way to the net where he too put on a show for the fans at The O2.

Murray and Soares won more than double the number of points in the match, never giving their opponents much of a chance. They broke Dodig in his first service game in each set, and ran away with it from there.

While the Croatian saved two break points from 0/40 at 1-1 in the second set, he could not fight off a third. Soares masterfully placed a return at Dodig’s feet, before taking the server’s reply and lobbing it over Granollers head, forcing the Spaniard into an error.

Murray and Soares, who secured the 2016 year-end No. 1 spot in the Emirates ATP Doubles Team Rankings in London, claimed 17 of the match’s final 21 points to gather plenty of momentum before their final round-robin match against the top-seeded pair of Lukasz Kubot and Marcelo Melo, who with a 2-0 record have already secured their spot in the semi-finals. Kubot and Melo clinched this season's year-end No. 1 Emirates ATP Doubles Team Ranking with their opening win Monday

"We played them quite a few times this year. It's always been close. Two of the matches have been close. Look, it's going to be difficult. They played a lot of great tennis since, like, March, won a bunch of tournaments, obviously feeling confident with their game," Murray said. "I think we're a great team. If we play our best, I think we're better than them. We might not win, but I'm still going to back us."

The sixth seed dashed to 6-0, 6-2 win against Belgian David Goffin, cruising in only 74 minutes to move to 2-0 in London. Dimitrov guaranteed his spot in the semi-finals, joining Roger Federer as the only two singles players who have secured their weekend reservations. The Bulgarian has also put himself in great shape to win Group Pete Sampras and face the second-place finisher of Group Boris Becker on Saturday.

“I think clearly I played a great match today,” Dimitrov said. “I think my focus was very good. I started the match well. I was using every opportunity. I took care of all of the balls that I had to. I won the most important points, especially in the first set.”

The first Bulgarian to qualify for the season finale in its 48-year history was dominant all day. He raced to a 3-0 lead in the first set, winning 12 of the first 15 points. Goffin had two chances on serve for 1-3, but Dimitrov pulled out the 15-point game and broke once more to win the first set.

Forty-eight minutes into the match, Goffin put himself on the scoreboard. But he never found the level that helped him to the biggest win of his career over World No. 1 Rafael Nadal at The O2 on Monday, partly because Dimitrov was pressing him all match. The sixth seed charged the net 17 times, winning 70 per cent of those points.

“I'm feeling okay. It was not the problem today. It was just a tough, tough match against Grigor, who played really well,” Goffin said.

“It was not easy for me to lose my serve from the start. It was tough for my confidence after that when it was 0-4. In the second, I had some opportunities to come back, to break back, but he was really solid. He served well.”

Dimitrov, who improved to 46-19 this season, said he played one of his best matches of the year. “This is definitely the one that sticks out in terms of consistency, focus, striking the ball, movement, agility, everything that I can possibly think... I work for those moments, too... They don't just come to you. Again, when you recognize that, you might as well make the most out of it,” he said.

The matchup seemed like it would follow a Nitto ATP Finals pattern so far this week and go three sets. Goffin had beaten Dimitrov during their most recent FedEx ATP Head2Head meeting, a three-sets win indoors in February at the ABN AMRO World Tennis Tournament in Rotterdam.

Instead, the Belgian, who still has a chance to qualify for the semi-finals, will try to finish Group Pete Sampras play with a win against Austrian Dominic Thiem on Friday. Goffin leads their FedEx ATP Head2Head rivalry 6-3.

“I have to now prepare for the next one... As a tennis player, normally you lose almost every week. Like I said, it's just another loss. The most important [thing] is to think about the next match,” Goffin said. “I have already an idea with the tactics against [Thiem] because I played so many times against him. We played a lot of good matches against each other.”

Watch highlights as Lukasz Kubot and Marcelo Melo take down Bob Bryan and Mike Bryan to become the second doubles team to earn their spot in the semi-finals. Photo Credit: Thomas Lovelock/ATP World Tour. Watch live tennis at TennisTV.com.

Rafael Nadal has clinched the year-end No. 1 Emirates ATP Ranking for a fourth time — to break a number of historical records — after beating #NextGenATP South Korean Hyeon Chung at the Rolex Paris Masters on Wednesday. The Spaniard will be presented with the ATP World Tour No. 1 trophy at the Nitto ATP Finals, to be held at The O2 in London from 12-19 November.

Nadal, who replaced Great Britain’s Andy Murray at No. 1 on 21 August, has enjoyed a stellar season, capturing six titles – including two Grand Slams and two ATP World Tour Masters 1000s — from 10 tour-level finals. At 31, Nadal is the oldest player to finish year-end No. 1 in Emirates ATP Rankings history (since 1973). Having previously finished at the top in 2008, 2010 and 2013, Nadal becomes the first player to hold, lose and regain the year-end No. 1 on three occasions.

He is also the first player to finish No. 1 four times in non-consecutive years, the first aged over-30 and the first to finish in the top spot four years since he last achieved the feat (2013). The nine-year gap between his first year-end No. 1 season (2008) and his last (2017) is also a record.

Nadal is the seventh player to finish the year at the pinnacle of men’s professional tennis on four or more occasions, following in the footsteps of Pete Sampras (6), Jimmy Connors and Roger Federer (5), Ivan Lendl, John McEnroe and Novak Djokovic (4). This is the 14th straight season that the year-end World No. 1 ranking has been held by a member of the ‘Big Four’ — Federer (2004-07, ’09), Nadal (2008, ’10, ’13, ‘17), Djokovic (2011-12, ’14-15) or Murray (2016).

"I’m very, very happy for everything," said Nadal in his on-court interview. "It has been an amazing year. One year ago, for sure I never dreamed about being World No. 1 again at the end of the season. It’s something that means a lot to me. But the season is not over."

Chris Kermode, the ATP Executive Chairman and President, said, "The year-end No.1 ranking is the ultimate achievement in our season, demanding the very highest standards in terms of excellence, consistency and endurance. By becoming – at the age of 31 – the oldest player in the game’s history to achieve this spectacular feat, Rafa has once again demonstrated his unwavering work ethic, determination and passion for the game. He continues to re-write the record books, and is a credit to our sport. On behalf of the ATP, we congratulate him on a phenomenal season."

The Spanish superstar, who ended the 2016 season early due to a wrist injury, has returned in 2017 playing some of the best tennis of his career. After finishing 2016 at No. 9, Nadal has made the biggest single-season jump to year-end No. 1 since Andy Roddick went from No. 10 in 2002 to No. 1 in 2003.

Nadal, who first ascended to No. 1 on 18 August 2008 at the age of 22, has spent four stints in top spot for a total of 152 weeks — 46 weeks between 18 August 2008 and 5 July 2009, 56 weeks from 7 June 2010 to 3 July 2011, 39 weeks between 7 October 2013 and 6 July 2014 and currently 11 weeks since 21 August 2017. Only Federer (302), Sampras (286), Lendl (270), Connors (268), Djokovic (223) and McEnroe (170) have spent more weeks at No. 1 since 1973.

This month, the Mallorcan is not only looking to win his first Rolex Paris Masters trophy, which would represent a record 31st ATP World Tour Masters 1000 crown, but is also aiming to clinch his first title at the Nitto ATP Finals, which he has qualified for on 13 straight occasions (seven appearances) since 2005.

The 31-year-old Nadal will be the oldest year-end No. 1 and first season-ending No. 1 over the age of 30 since the Emirates ATP Rankings were established in 1973. It is his fourth time finishing atop the Rankings, adding to 2008, 2010 and 2013.

Roger Federer has pushed Nadal all the way in the battle to finish atop the rankings, with both players enjoying remarkable comebacks in 2017. But with Federer forced to withdraw from Paris, Nadal needed just one more win to finish No. 1.

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“I’m very, very happy for everything,” said Nadal in his on-court interview. “It has been an amazing year. One year ago, for sure I never dreamed about being World No. 1 again at the end of the season. It’s something that means a lot to me. But the season is not over.”

It wasn’t plain sailing for Nadal against the 21-year-old Chung, who is due to feature at the inaugural Next Gen ATP Finals in Milan next week. After breaks were exchanged in the early stages, Nadal then rallied from a 0/40 deficit before breaking Chung to lead 4-2.

However, with Nadal serving for the set in the ninth game, his South Korean opponent broke back and levelled at 5-5. The Spaniard eventually got over the line in the first set as he opened up a 0/40 lead on Chung’s serve in the 12th game and clinched it with a forehand winner as the match ticked into the hour mark.

After Chung fended off four break points in the fourth game of the second set, Nadal made his move with a break in the ninth game before sealing victory in one hour and 49 minutes.

Nadal is looking to win his 31st ATP World Tour Masters 1000 crown this week, and third of the season after victories in Monte-Carlo and Madrid. The left-hander is hoping to add Paris to his illustrious collection, after finishing runner-up at the AccorHotels Arena in 2007 (l. to Nalbandian).

The 30-year-old Haase, who reached his first ATP World Tour Masters 1000 semi-final in the summer in Montreal (l. to Federer), overcame the 20-year-old Zverev in one hour and 33 minutes. The right-hander won 77 per cent of his service points and broke Zverev four times as he set up a clash with either Joao Sousa or Nitto ATP Finals contender Juan Martin del Potro.

Zverev will look to cap his standout season in style when he makes his debut at the Nitto ATP Finals in London, beginning 12 November. The German has won two Masters 1000 crowns this season, in Rome and Montreal, and also lifted trophies in Montpellier, Munich and Washington.

Ninth-seeded American John Isner battled hard to keep alive his slim chances of qualifying for next month’s season finale by hitting 29 aces in beating Argentina’s Diego Schwartzman 7-6(2), 6-7(11), 6-3 over two hours and 35 minutes. Isner could not convert match point opportunities on his serve at 6/5, 8/7 and 10/9 in the second set tie-break. Schwartzman ends the best season of his career with a 39-28 match record. Isner will now face sixth-seeded Bulgarian Grigor Dimitrov, a first-time Nitto ATP Finals qualifier this year, or Richard Gasquet of France.

Lucas Pouille continued his late push to qualify for London as he defeated Feliciano Lopez 6-3, 6-4 in 58 minutes. The Frenchman is coming off the biggest title of his career in Vienna, where he defeated Jo-Wilfried Tsonga in the final, and must reach the final in Paris if he is to have a chance of clinching one of the last two spots in London.

In action later on, Rafael Nadal will clinch the year-end No. 1 spot in the Emirates ATP Rankings with victory over Hyeon Chung, while London contenders Tsonga, Goffin, Anderson and del Potro are all in the hunt for crucial points.

Rafael Nadal can clinch the year-end No. 1 ranking for the fourth time by defeating #NextGenATP player Hyeon Chung at the Rolex Paris Masters on Wednesday. Nadal, 31, bids to become the oldest year-end No. 1 and first year-end No. 1 over the age of 30 since the Emirates ATP Rankings were established in 1973. He also finished 2008, 2010 and 2013 atop the rankings. If Chung upsets Nadal, the Spaniard will get a second chance to clinch at the Nitto ATP Finals November 12-19.

Tsonga and Benneteau were among the tournament-record five Frenchmen who reached the third round in 2009. As many as six can make it that far this year, including Lucas Pouille and Adrian Mannarino. Pouille won the biggest championship of his career in Vienna on Sunday and became the only player in 2017 with titles on three surfaces. He faces Feliciano Lopez on Court Central, while Mannarino meets No. 1 Belgian David Goffin in a possible preview of the Davis Cup final.

The Spaniard currently occupies the final qualifying spot in the Emirates ATP Race To London, as he looks to make his debut at the year-end championships, but now must wait and see how Kevin Anderson, Juan Martin del Potro, Jo-Wilfried Tsonga and Lucas Pouille perform at the final ATP World Tour Masters 1000 tournament of the season.

Home favourite Mahut, who battled past Vasek Pospisil in the first round, defeated the eighth-seeded Carreno Busta 6-4, 6-1 in just 86 minutes. The 35-year-old Mahut, a wild card entrant, saved eight of the nine break points he faced as he avenged his US Open loss to Carreno Busta.

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Serbian qualifier Filip Krajinovic recorded just his second tour-level match win of 2017 — and his first victory at an ATP World Tour Masters 1000 tournament in two-and-a-half years — to end American Sam Querrey’s quest for a place at next month’s Nitto ATP Finals. Krajinovic will now face Mahut for a spot in the quarter-finals.

Krajinovic, whose sole victory at Masters 1000-level had come against compatriot Dusan Lajovic at Miami in March 2015, knocked out No. 10 seed Querrey 6-4, 6-4 in 79 minutes. Querrey, who had led 2-0 in the second set and struck 11 aces, ends his 2017 campaign with a 36-21 match record, including two ATP World Tour titles.

Querrey started the week in the French capital at No. 11 in the Emirates ATP Race To London on 2,525 points – only 80 points behind Carreno Busta (2,605).

Dominic Thiem, who has already clinched his spot in the eight-man field, was made to work for a win his second-round opening match. The fifth-seeded Austrian prevailed against Peter Gojowczyk 6-4, 6-7(3), 6-4 after two hours and six minutes. Thiem was unable to serve out the match in the second set as the German lucky loser fought off match points to force a tie-break, but clinched the victory by capitalising on his first break point of the decisive set.

Thiem awaits the winner between London hopeful Anderson and Spaniard Fernando Verdasco. Anderson began the week at No. 12 in the Race standings and would qualify should he win his first Masters 1000 title this week.