Britain's defending Olympic champion Andy Murray pulled out of the Tokyo 2020 men's singles tournament on Sunday ahead of his first-round match.
The 34-year-old, who had been due to play Canada's Felix Auger-Aliassime, was sidelined by a thigh strain.
Murray has been replaced in the draw by Australian Max Purcell.
The Scot will continue to compete in the men's doubles tournament with Joe Salisbury, Team GB said, the pair having won their opening match on Saturday.
"I am really disappointed at having to withdraw but the medical staff have advised me against playing in both events," a statement from Murray read.
"I have made the difficult decision to withdraw from the singles and focus on playing doubles with Joe."
Murray won Olympic gold on Wimbledon's Centre Court at the London 2012 Games, and defended his title in Rio.
He underwent hip surgery in 2018 and 2019, and missed the Australian Open at the start of this year after contracting COVID-19.
Teenager Gukesh Dommaraju of India became the youngest chess world champion by beating defending champion Ding Liren of China on Thursday in a dramatic turn of events in the last game of a 14-game match in Singapore.
Saudi Arabia will host the FIFA World Cup in 2034 while the 2030 edition will be held in Spain, Portugal and Morocco, with one-off matches in three South American countries.
FIFA is set to confirm the hosts of the 2030 and 2034 men's World Cups on Wednesday, with a three-continent, six-nation bid led by Morocco, Spain and Portugal to be awarded the former and the latter going to Saudi Arabia.
Following arguably the most dominant year of golf since Tiger Woods was in his prime, Scottie Scheffler received the PGA Tour Player of the Year award on Tuesday night.
European Ryder Cup stars Robert MacIntyre and Tyrrell Hatton, and Major winner Adam Scott are the latest stars to confirm their return to the Hero Dubai Desert Classic, while PGA TOUR winner Akshay Bhatia will make his debut at the Emirates Golf Club from January 16-19.