"I wasn't expecting him to be so nervous. It was really nerve-wracking watching him be so nerve-wracked because I'm just kind of there observing, not saying a thing, watching as a fly on the wall," he said.
Federer, who turns 43 in August, said he was happy to let his feelings show on screen.
"It's not like I'm crying through 1.5 hours of the film, you know? It's a tough watch, but a good one," he said.
"You see the struggles that we go through and also how vulnerable we are in many ways and how much the fans and the spotlight means to me," he said.
"It's such a beautiful moment in time that I'm really curious to find out how people will like it. We'll see."
"Federer: Twelve Final Days" starts streaming on Prime Video on June 20.
Published 14 June 2024, 00:40 IST