Great Britain's two-time defending Olympic champion Andy Murray announced on Sunday that he has withdrawn from the men's singles with a quad strain.
Murray, the first male player to win back-to-back tennis golds following triumphs in London and Rio, has been battling with a succession of injuries since undergoing hip resurfacing surgery in January 2019.
The former world No 1 was scheduled to play Canada's Felix Auger Aliassime in the first round at the Tokyo Olympics. He was replaced in the draw by Australia's Max Purcell.
Murray confirmed that he will continue to play in the men's doubles alongside Joe Salisbury. The pair won their opening match of the competition on Saturday against second seeds Pierre-Hugues Herbert and Nicolas Mahut of France.
"I am really disappointed at having to withdraw but the medical staff have advised me against playing in both events, so I have made the difficult decision to withdraw from the singles and focus on playing doubles with Joe," Murray, 34, said in a statement.
"The decision follows consultation with medical staff in relation to a quad strain."
Purcell, ranked No 190, made the most of his last-minute opportunity by producing a shock 6-4, 7-6 win over world No 15 Auger Aliassime.
The Australian will be joined in the second round by Germany's Alexander Zverev after the world No 5 eased past Chinese Taipei's Yen-Hsun Lu 6-1, 6-3.
Despite Murray's withdrawal, Great Britain still have a representative in the draw after Liam Broady reached the second round with a 7-5, 6-7 6-2 win over Argentina's Francisco Cerundolo. He will play Poland's Hubert Hurkacz for a place in the third round.