Roger Federer has withdrawn from the Tokyo Olympics because of a setback to his knee suffered during the grass-court season.
Olympic gold in singles is one of the few honours missing from Federer's glittering resume, the 20-time grand slam champion having won silver in 2012, losing the gold medal match to Andy Murray less than a month after beating the Briton in the Wimbledon final.
While Murray will be in Tokyo to attempt to defend his title again having successfully retained it in 2016, Federer – a doubles gold medallist in 2008 – has elected not to make the trip to Japan.
"During the grass-court season, I unfortunately suffered a setback with my knee, and have accepted that I must withdraw from the Tokyo Olympic Games," Federer wrote in a statement on Twitter.
"I am greatly disappointed, as it has been an honour and highlight of my career each time I have represented Switzerland.
"I have already begun rehabilitation in the hopes of returning to the tour later this summer. I wish the entire Swiss team best of luck and I will be rooting hard from afar. As always, Hopp Schwiz!"
Federer missed most of the 2020 season due to persistent right knee problems that led him to undergo two surgeries.
The length of his recovery forced Federer to miss this year's Australian Open but he made his return to the tour in time for the French Open, reaching the fourth round before withdrawing to focus on the grass-court season.
Yet he was stunned by Felix Auger-Aliassime in the second round in Halle and was often unconvincing in progressing to the quarter-finals at Wimbledon, where his quest for a ninth title was ended by Hubert Hurkacz, the Pole becoming the first player to win a set 6-0 against Federer at the All England Club.
The 39-year-old's withdrawal makes him the latest tennis big name to pull out of the Tokyo Games. On the men's side, Rafael Nadal and Dominic Thiem decided against competing, while Serena Williams confirmed before her first-round retirement at Wimbledon that she had no plans to play at the Olympics.
World number one Novak Djokovic has said he is "50-50" on going for his first Olympic title. Having won all three majors so far this year, Djokovic is in prime position to become the first man to do the 'Golden Slam' in the same season. Steffi Graf achieved the feat in 1988, with a sweep of the majors followed by her victory at the Seoul Olympics.