World number one Ashleigh Barty crashed out of the Olympic women's singles tennis tournament in the opening round on Sunday, losing 6-4, 6-3 to Spain's Sara Sorribes Tormo in Tokyo.
Barty, the reigning Wimbledon champion, dropped serve twice in each set as 48th-ranked Sorribes Tormo made just five unforced errors to the Australian's 27 to earn a shock win.
Two-time defending Olympic tennis champion Andy Murray, meanwhile, withdrew Sunday from the men's singles tournament due to a muscle injury, Team GB said in a statement.
Murray, 34, will stay in Tokyo to play doubles with Joe Salisbury. The pair won their opening match of the competition on Saturday.
"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 said in a statement.