That is according to his Miami Open final opponent John Isner.
Federer beat Isner in straight sets to win his 101st ATP title in Miami last week.
The 33-year-old American played the final stages of the final through injury, but felt little regret considering the quality of his opponent.
“I consider myself very fortunate,” Isner told ATP.com.
“I could have hurt myself in my second match and had to have probably lost that match or pulled out of the tournament.
“There was just one match to go and of course I was thrilled to be in the final.
“I wanted to put on a little bit of a better show out there but I was also up against the greatest player of all-time.”
Isner was almost forced to retire during the final set in his clash against Federer with a stress fracture in his foot.
However, the former Wimbledon semi-finalist managed to play through the pain, although it has no left him with some time on the sidelines.
“It was just any time I put weight on my left foot,” he continued.
“Serving puts a lot of weight on my left foot, that’s my predominant leg when I’m serving.
“Any other movement that required any sort of push off my left leg was pretty excruciating.
“It was a tough, tough feeling because there’s nothing you could do.
“There’s no hiding it out there.
“You can’t play through that pain, either. You’re stuck out there.
“It’s a pretty miserable feeling.”