He said it took him 6 to 9 months before he felt completely back to normal.
In his first interview at Wimbledon 2008 he said in response to a question,
Q. "How would you compare your game now to your game a year ago this time?"
ROGER FEDERER: "Well, now it's better again. Maybe at the beginning of the year, like I said, I felt a little slow. Just felt a little bit rattled due to the sickness I had.
But today I feel as good again as last year. You know, one year has gone by. I've played plenty of matches. I feel like I'm playing well, which is good."
Later when asked he said,
Q." Would you say you're playing better than ever this year, right now?"
ROGER FEDERER: " Well, I mean, my way to the final's been great. You know, I cannot do much better than this. But I've just been playing consistently well. I wasn't maybe pushed to the degree where I have to say I played my best tennis ever.
I just think it's been good tennis so far. You know, if I were to win tomorrow, on Sunday, then maybe I can say I've been playing my best ever.
But at the moment I think it's a little bit too early."
"I really feel like I'm playing as good as the last few years."