The inconstant Australian, finalist this season at Wimbledon, winner in Washington and moved up to 20th place in the ATP rankings, explained to the press that his retirement was a "heartbreaking" decision but that he had no choice.
Kyrgios pointed out that he had "played fantastic tennis all season", but it had taken a toll on his physique.
"I've been dragging a knee problem since the US Open, I went home but probably didn't stop long enough, to be honest, I started training straight away," he said. he says.
"It's heartbreaking. When your body lets you down, it's not a good feeling," Kyrgios, 27, continued, without specifying whether his season was over or not with a few tournaments left to play.
Kyrgios, who had beaten Poland's Kamil Majchrzak in three sets the day before and who was also engaged in doubles with his compatriot Thanasi Kokkinakis, clarified that his knee had "not really" bothered him until then but that he had felt pain when warming up on Friday.
"It's probably a case of overload" of work, he said.
"It's almost over-excited to go on the court, and maybe a little too much practice."
His abandonment propels Taylor Fritz, seeded number 3 in Tokyo, into the semi-finals, where he will face Canadian Denis Shapovalov, seeded N.7, winner at the end of the program from Croatian Borna Coric 6-4, 6- 3.
At the top of the table, which emerged with the defeat in the first round of the Norwegian Casper Ruud, seeded N.1, the semi-final will face the American Frances Tiafoe, recent semi-finalist at the US Open, to South Korean Kwon Soonwoo (120th player in the world).
The American, seeded N.4, made short work of Serbian Miomir Kecmanovic in the quarter-finals 6-0, 6-4 in 71 minutes and will start as favorite.
"Great tennis today," he commented.
"I was moving really well and hitting the ball really well from the baseline."
© 2022 AFP