British number one Jack Draper ran out of steam as Spanish third seed Carlos Alcaraz moved into the Australian Open quarter-finals.
Draper, seeded 15th, retired when he was trailing 7-5 6-1 against four-time major champion Alcaraz on a hot day in Melbourne.
The 23-year-old left-hander needed treatment off the court after the first set before abandoning the match at the end of the second.
He held both hands up to the crowd by way of an apology before going off Rod Laver Arena to a warm ovation.
"It is not the way which I want to win," said Alcaraz.
"I'm happy to play another quarter-final here in Australia, but I am sad for Jack – he doesn't deserve to be injured.
"I wish him a speedy recovery."
Draper, who came through three gruelling five-setters to reach the fourth round, was the only Briton to reach the last 16 of the men's or women's singles.
Alcaraz, 21, was far from his best during their contest but continues his bid to become the youngest man in the Open era to complete the career Grand Slam.
