The British Jack Draper, the first seed, ran out of effort, with the Spanish Carlos Alcaraz, the third seed, qualifying for the quarter-finals of the Australian Open.
Draper, seeded 15th, retired when trailing 7-5, 6-1 to four-time Grand Slam champion Alcaraz on a hot day in Melbourne.
The 23-year-old, who uses his left hand, needed treatment off the court after the first set before abandoning the match at the end of the second set.
He raised his hands to the crowd as an apology before walking out of Rod Laver Arena to a standing ovation.
“This is not the way I want to win,” Alcaraz said.
“I'm happy to play a quarter-final again here in Australia, but I'm sad for Jack – he doesn't deserve to be injured.
“I wish him a speedy recovery.”
Draper, who overcame three tough five-setters to reach the fourth round, was the only Briton to reach the round of 16 in men's or women's singles.
Alcaraz (21 years old) was not far from his best levels during the competition, but he continues his quest to become the youngest player in the open era to complete his career in the four major tournaments.
The back-to-back Wimbledon champion, who also won the 2022 US Open and 2024 French Open, could face Novak Djokovic in the next match.
Serbian Djokovic, who is seeking to increase his record by winning the men's singles title for the 11th time in Australia, will play with Czech Jiri Lehka later on Sunday.
