Roger Federer, who has won a doubles gold alongside fellow Swiss Stan Wawrinka, is still waiting to get his hands on an Olympic singles gold.
Novak Djokovic received treatment before the start of the third set against Stan Wawrinka but soon threw in the towel, the 6th time he has retired at a Grand Slam tournament.
World No.1 Novak Djokovic was trailing 4-6, 5-7, 1-2 when he quit, having received treatment on his troublesome left shoulder before the start.
Novak Djokovic was captured on video having a talk with a fan during his pre-match practice session.
Novak Djokovic will meet Stan Wawrinka, the man who beat him in the US Open final three years ago, for a place in the last eight.
Rafael Nadal remains well behind world number one Novak Djokovic in the ATP rankings despite winning a record 12th French Open title.
Rafael Nadal is chasing a 12th French Open title while 2009 champion Roger Federer is playing in the tournament for the first time since 2015.
Roger Federer admitted he struggled to get past the talented Gael Monfils.
Roger Federer booked a round of 32 match with Serbian Filip Krajinovic who surprised three-time Grand Slam winner Stan Wawrinka.
Roger Federer, who has won their last five encounters, including the 2017 Indian Wells final, said an in-form Stan Wawrinka is an opponent to be wary of.
Nick Kyrgios out-lasted Wawrinka 7-5, 6-7 (3/7), 6-4 to book a meeting with John Isner for a place in the final.
Novak Djokovic defeated Jo-Wilfried Tsonga 6-3, 7-5, 6-4 in straight sets.
Novak Djokovic will be up against Spain's Roberto Bautista Agut in the semi-final.
Marin Cilic crashed out of the Japan Open in a shock 3-6, 6-4, 7-6 defeat to Germany's Jan-Lennard Struff in the first round.
Stan Wawrinka has been struggling to find his best form since returning to the ATP Tour after two operations on his left knee a year ago.
Andy Murray lost 5-7, 6-2, 4-6, 4-6 to Spain's Fernando Verdasco in US Open second round.
Former US Open champions Stan Wawrinka and Svetlana Kuznetsova received wildcards into the event on Tuesday along with two-time Australian Open winner Victoria Azarenka, tournament organisers announced.
A 45-minute rain interruption did little to stop the progress of Rafael Nadal on Thursday at the Toronto Masters as he defeated Stan Wawrinka 7-5, 7-6 (7/4) to reach the quarter-finals.