Originally Posted by Sartorius
This pretty much. Federer's "tennis bag" (what he can do, how well he does it) is bigger and better: I think this is what Cahill and Federer himself is referring to. But his consistency has naturally suffered.
A lot of people talk about Federer's superior game in his heyday and with good reason; but they overlook the fact that what made him successful was ultimately his ability to play well (use his tennis bag to its fullest so to speak) almost all the time, during a match and during an entire year.
This is exactly what I was getting at. He's got more tools at his disposal, but he's no longer has the stamina be it mental or whatever to have them all up and running day after day and against anyone.