“Dominic won a Slam in the meantime. Rafa, Novak are still where they are. You would think that the game has improved again.
“For me, that’s going to be an extra challenge, extra hard for me to find that level, but I guess I knew from the get-go it was never going to be simple, regardless of whether I was going to be out for three months or almost a year and a half.”
Federer, who is eighth in the world rankings, will face Spain’s Pablo Andujar in Geneva on Tuesday.
He said: “At the moment I am healthy and able to get matches again under my belt, getting used to being out on court, serving for hours and then recovering and doing the same thing again, that will all just increase my confidence.
“I feel really comfortable with Geneva, Paris, Halle, Wimbledon and I think it’s a good schedule for me to come back this way.”