Roger Federer says he will be sidelined for “many months” as he prepares to have further knee surgery.
The 40-year-old Swiss, a 20-time Grand Slam champion, had two knee operations last year.
In a video post on Instagram, Federer said he hoped the surgery would give him “a glimmer of hope” to return to action.
He was knocked out in the quarter-finals at Wimbledon in July and then missed the Tokyo Olympics.
“I’ll be on crutches for many weeks, and also out of the game for many months,” Federer, who turned 40 a week ago, said on Sunday evening.
“It’s going to be difficult in some ways but, at the same time, I know it’s the right thing to do because I want to be healthy, I want to be running around later as well again.
“I also want to give myself a glimmer of hope to return to the tour in some shape or form.