Whenever Federer get high balls to his backhand (courtesy Nadal, etc), I hardly see Federer being able to hit the wide crosscourt backhand consistently. His comfort shot in this case lands somewhere in the middle of the court, as in such rallies, the down-the-line (over the high part of the net) or a wide crosscourt do not seem to be his comfort shots. I am not saying Federer lacks this shot, he played this shot amazingly well in the WTF final against Nadal, but those were few and far in between. It was not Federer's Go-To shot!
Compare that to a Djokovic/Murray/Nalbandian/Davydenko, who are able to keep Nadal much more honest, as Nadal always has to keep an eye for that wide crosscourt backhand. Against Nadal, a wide crosscourt pushes Nadal completely towards his forehand side, which then opens up the court on Nadals backhand side.
Against Federer, Nadal comfortably runs around most of his backhands, since he knows he can lean on that side much more. You can almost see in all the recent Djokovic matches, Nadal is almost standing in the middle of the court, whereas if you see any of his matches against Federer, you would see that his default position is halfway to his deuce court, ready to run around his backhand.
Is it difficult for a player with a one-handed backhand to hit that shot effectively? But then you see a Gasquet or a Wawrinka pulling that shot quite consistently. Even against Lopez today, you could see that Federer was hardly able to rip any wide cc backhands, whereas Lopez was doing that consistently, making Federer run to his Forehand side.
Federer has added a few shots in the past to his arsenal (for regular use in match play), like his Drop Shots, then the wide-serve to Nadals backhand on the Deuce court, do you think this is the shot we would see him using more often, and more consistently?
i dont think he has the shoulder strenght to execute that shot more often than not