I would imagine now that for guys like Duval or IBF, it's much more mental. While not at the same level as those guys, I hurt my back my first season of college golf, and once the physical injury had healed, it took me a real long time to get my mental game back to where I had the confidence to hit the shots I used to.
A lot of the time the problems of great players stems from their inability to drive the golf ball into play, especially under pressure, (get the "driver yips" as some say), and it's mostly the confidence to make an aggressive, good swing that they are lacking.
Stew