Wimbledon champion Roger Federer saved two match points before defeating Andre Agassi at the ATP Masters Cup.
The world number two will withdrawal from the tournament if the tendinitis in his knees does not improve.
Images from Day 3 of the US Open, at Flushing Meadows, New York.
Mahesh Bhupathi and Rohan Bopanna overcame a late resistance from Santiago Gonzalez and Christopher Kas to move to the quarter-finals of the ATP Madrid Masters.
Roger Federer had not beaten a top 10 player since January until he overcame Juan Martin Del Potro in the Paris Masters quarter-finals on Friday to secure a much-needed confidence boost.
Continuing his impressive comeback post a shoulder surgery, Somdev Devvarman erased a one-set deficit to beat World No. 78 Evgeny Donskoy in his opening round of the ATP Miami Masters.
Novak Djokovic began his bid to hold on to his number one ranking with an easy win over Gilles Muller in the Paris Masters second round while Andy Murray struggled through and Stan Wawrinka faltered on Wednesday.
Mahesh Bhupathi and Rohan Bopanna may meet Leander Paes and Radek Stepanek in the summit clash of the Shanghai Masters after reaching the semifinals of the elite ATP tournament on Friday.
Robin Soderling signalled his intentions for the season-ending ATP World Tour Finals when he claimed his maiden Masters title with a clinical 6-1, 7-6 defeat of local favourite Gael Monfils in Paris on Sunday.
The eight-man Masters Cup will be held for the third year at Qi Zhong Stadium from November 11-18.
He is the sixth American and just the 13th player in the history of the ATP rankings to finish the year at the top.
Mahesh Bhupathi is the lone Indian survivor at the ATP Rogers Cup as Somdev Devvarman, Leander Paes and Rohan Bopanna crashed out of the Masters Series event following defeats in their respective draws.
Bhupathi and Mirnyi will take on Cyril Suk and Martin Damm of Czech Republic in the semi-final.
The prestigious end-of-season Masters Cup will switch from Shanghai to London from 2009, the ATP men's tennis tour announced on Tuesday.
The Indian pair of Mahesh Bhupathi and Rohan Bopanna crashed out of the ATP Madrid Masters after losing their semifinal match to Robert Lindstedt of Sweden and Horia Tecau of Romania in Madrid.
The Indian challenge in the ATP Paris Masters tennis tournament ended after Mahesh Bhupathi and Leander Paes, along with their respective partners, crashed out of the doubles event following unexpected second-round defeats.
Rafael Nadal dug deep to beat mercurial wildcard Nick Kyrgios 7-6(0), 5-7, 6-4 in a blockbuster quarter-final match that lived up to the hype at Indian Wells on Thursday.
Frenchman Jo-Wilfried Tsonga staged a spectacular third set comeback to stun world number one Roger Federer 7-6, 1-6, 7-6 on Friday and reach the semi-finals of the Montreal Masters. Juan Martin Del Potro ended Nadal's Montreal title defence with a clinical 7-6, 6-1 win.
Nadal says Wimbledon ban on Russian and Belarusian players unfair
Leander Paes and Lukas Dlouhy advanced to the quarter-finals of the Paris Masters after registering a tough three-set win over American pair of John Isner and Sam Querry in Paris.
All the results from the matches played in the BNP Paribas Paris Masters on Tuesday
With 1,500 points available for an undefeated champion next week, the tournament could produce a thrilling climax with Murray and Djokovic, who have never met at the O2, facing off in the final for the year-end number one ranking.
Paes and his Czech partner Radek Stepanek beat Jerzy Janowicz and Lukasz Kubot while Bopanna and Edouard Roger-Vasselin got the better of Andreas Seppi and Mikhail Youzhny in second round matches.
Mahesh Bhupathi and Mark Knowles eased into the semifinals of ATP Montreal Masters after scoring a 6-3 6-4 win over the Polish pair of Mariusz Frystenberg and Marcin Matkowski.
Rohan Bopanna and Aisam-ul Haq Qureshi failed to get past the formidable United States' combination of Mike and Bob Bryan, losing in straight sets in the second round of the ATP Rome Masters, on Thursday.
Sharapova was broken in the first game but fought back to draw level before going on to take the first set with a hold to love.
A season that produced the biggest shake-up in men's tennis for more than a decade draws to a close next week with three ATP World Tour Finals debutants striving to sign off breakthrough years with a large exclamation mark.
Leander Paes and Radek Stepanek won the ATP Shanghai Masters, their third tour-level title of the season, after defeating Mahesh Bhupathi and Rohan Bopanna 6-7(7), 6-3, 10-5.
Sania Mirza and Martina Hingis of Switzerland stormed into the semi-finals of the Rome Masters with a straight-set victory over Julia Goerges and Silvia Soler-Espinosa on Thursday.
Wawrinka's last ATP title came in 2017 before the former world number three underwent knee surgery.
Novak Djokovic pocketed a $1.6-million bonus just for turning up on court on Wednesday before making light of recent shoulder pains to beat Croatian Ivan Dodig 6-4, 6-3 in the second round of the Paris Masters.
World number one Novak Djokovic recovered from a first-set loss to overcome Germany's Mischa Zverev while Britain's Andy Murray swept past Belgium's David Goffin to reach the Shanghai Masters semi-finals on Friday.
Paes and the Czech Republic's Rikl defeated fifth seed Australian duo Wayne Arthurs and Paul Hanley 6-3, 6-2.
Eighth seed American Andy Roddick has pulled out of the Toronto Masters because of illness, the ATP Tour said on Tuesday.
Three-times champion and world number one Novak Djokovic has been drawn in a group with U.S. Open champion Marin Cilic in next week's season-ending ATP World Tour Finals in London.
Top seed Carlos Alcaraz snapped Daniil Medvedev's 19-match win streak with a 6-3, 6-2 rout in the Indian Wells final on Sunday.
Four more performances like that at the O2 Arena this week should guarantee Andy Murray will end 2016 leading the pack.
Novak Djokovic and Roger Federer notched up contrasting victories to reach the Shanghai Masters quarter-finals on Thursday while David Ferrer fought back from a set down to knock out Andy Murray.
Australian Kyrgios was beaten in his first match in Lyon on Tuesday by Argentina's 94th-ranked Nicolas Kicker -- serving nine double faults during a 2-6, 6-4, 6-2 defeat.