Switzerland's Roger Federer is latest big name in tennis to withdraw from the Tokyo Olympics after the 20-times Grand Slam champion revealed he had picked up a knee injury during the grass court season.
Federer, who turns 40 next month, had two knee surgeries in 2020 which resulted in more than a year of rehabilitation, with the Swiss returning to action in March - 13 months after his Australian Open semi-final exit last year.
He withdrew from the French Open last month despite winning his third round match to save himself for the grass court season, where he sought a record-extending ninth title at Wimbledon, but was beaten in the quarter-final by Hubert Hurkacz.
"During the grass court season, I unfortunately experienced a setback with my knee, and have accepted that I must withdraw from the Tokyo Olympic Games," Federer said 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 the best of luck and I will be rooting hard from afar."
Federer won the gold medal in the doubles at the 2008 Games in Beijing when he partnered with Stan Wawrinka while he had to settle for silver in the singles four years later in London when he was beaten by Briton Andy Murray on Wimbledon's Centre Court.
He was also Switzerland's flag bearer at the 2004 and 2008 Games.
Federer joins a list of big names to skip the July-August Tokyo Games after Rafa Nadal, Dominic Thiem, Wawrinka, Nick Kyrgios, Serena Williams, Simona Halep and Bianca Andreescu also decided not to compete.
Novak Djokovic, who has won the first three Grand Slams of the year, said he was "50-50" about competing in Tokyo following the organisers' decision to ban fans from attending and the restrictions on the number of people he can take to the Games.
COVID-19 forces Konta out of Games
Meanwhile, Johanna Konta has also withdrawn after a positive test for COVID-19 affected her preparations.
Konta was forced to withdraw from Wimbledon a day before the Grand Slam after a member of her team tested positive for COVID-19. But the 30-year-old said she also developed symptoms while self-isolating before testing positive for the virus.
"As a result, I have been unable to train for the last two and a half weeks and sadly, this has put my body in a situation where I am unable to ask it to be fully ready in time for the Olympic Games in Tokyo," Konta said on Twitter.
"This is a heart-breaking reality for me, as representing Team GB at the Olympic Games in Rio in 2016 is one of my most treasured memories from my career so far.
"I'll be doing my best to get myself back to full health and fitness and ready to be competing again soon. During this time, I'll also be glued to my TV cheering on my fellow Team GB athletes competing in Tokyo and I hope you will all join me."
Konta reached the quarter-finals at the 2016 Rio Games, losing in straight sets to Germany's Angelique Kerber.
Her withdrawal from Wimbledon was a cruel blow as she had won the Nottingham grasscourt title in the build-up to the Grand Slam.