Washington - Three-time Grand Slam champion Andy Murray withdrew from the ATP Tour's Washington Open on Friday, citing fatigue after a 03:00 finish that left him crying into a towel.
The 31-year-old British star, who returned in June from an 11-month layoff with a right hip injury, also withdrew from next week's ATP Toronto Masters, also citing the drain from three gruelling three-set victories over more than eight hours on the US capital hardcourts.
"I'm exhausted after playing so much over the last four days, having not competed on the hard courts for 18 months," Murray said.
"I also need to be careful and to listen to my body as I come back from a long-term injury."
Murray, whose last prior hardcourt appearance was in March 2017 at Indian Wells, played only two June grasscourt events in his comeback prior to coming to Washington, where he played three of the week's four longest matches.
"I've played quite a few matches this week in Washington and I need to be smart with my rest and recovery as I come back from injury," Murray said.
The Scotsman, whose next US Open hardcourt tune-up event will be the Cincinnati Masters starting August 13, was upset following his 6-7 (5/7), 6-3, 7-6 (7/4) victory over Romanian Marius Copil at having been forced to play from midnight to 03:00 - the latest finish in the Washington event's 50-year history.
"I don't think I should be put in a position like that," Murray said after the victory.
"(My body) doesn't feel great right now.
"Finishing matches at three in the morning isn't good for anyone involved in the event, players, TV, fans, anyone. When you're expected to come back and perform the next day, I think that's unreasonable."
Murray said in the pre-dawn hours he might withdraw, adding, "I don't know how players are expected to recover. It's a very difficult position to be coming back from a long injury to be finishing matches at 03:00 in the morning."
In a statement released by the event, Murray expressed more disappointment at being unable to continue.
"I'm gutted not to be playing and I'd like to thank the tournament and all the fans," he said.
"There are lots of positives to take from this week, so I'll take some time to rest and recover and then head to Cincinnati early to prepare and get ready."
After the match, a shattered-looking Murray wept into a towel for several minutes, calling it, "just the emotions coming at the end of an extremely long day and a long match," Murray said.
Murray's pull-out handed a walkover into the semi-finals to 19-year-old Australian Alex De Minaur, who ousted 11th seed Steve Johnson and eighth seed Chung Hyeon, both on Thursday.
Tournament director Keely O'Brien had told the Washington Post she wanted Murray to play, citing his role model status.
"Certainly if he can't play because of his injury, that's one thing. But he's a fighter, and he doesn't give up, and he needs to have everyone see that," she said.
After Murray's announcement, O'Brien said she expected Murray would return next year.
"I am so grateful that Andy, an incredible champion, came back to DC to begin what we all know will be a great comeback," she said.
"I sincerely respect his decision and know that his health and recovery process is his top priority, as it should be."