A nice tidbit from tennis.com:
Federer’s trainer: Roger hasn’t lost a step
Matt Cronin | Friday, November 02, 2012
Pierre Paganini, the longtime fitness trainer of Roger Federer, tells the New York Times that the 31-year-old has not lost any speed.
“I’m convinced that he has not lost a step,” Paganini said. “You also can’t forget that Roger has a quality of anticipation that is enormous. In tennis, you don’t only need to be fast. You need to run cleanly and use speed intelligently, and Roger is very intelligent in this department. It’s court vision, anticipation, maturity.”
Paginini added that the reason why Federer has never suffered a major injury is because he knows recovery is an important part of the process.
“So for him it’s natural to recover after a series of tournaments and then he’s even more motivated to start training again,” he said. “What I find interesting is that he is just as motivated now as he was as a junior. I’d say even more so for the physical training. When he was young, he was an artist who wanted to be an artist. Now he’s an artist who knows exactly what he needs to do to express his virtuosity.”
Not sure I'd completely agree with Paginini - certainly moving to his right, Fed is noticeably slower on some days