Roger Federer says his decision to retire came after he "stopped believing" he could continue playing because of injuries.
The Swiss, 41, has not played since Wimbledon 2021, after which he had a third knee operation.
"The last three years have been tough to say the least," he told BBC Breakfast.
"I knew I was on very thin ice for the last year ever since I played Wimbledon.
"I tried to come back but there was a limit to what I could do. And I stopped believing in it, to be honest."
Federer said he had a scan a few months again and it was "not what I was hoping for", adding: "Very quickly we realised this was it.