I really depends on this injury and how it will affect his game, mentally and physically so it's tough to call.
It will all depend on the quality of Fed's 1st serve.
If it's off, for whatever reason (and please spare me the 'injured'-excuses), he'll have a bloddy hard job to face, if it does indeed works... woe to all of his opponents.
As for the injury excuse cited above, how any Nadal fan is not embarrassed to keep talking about sparing excuses for injuries is beyond me. But then again I support a fair and honest guy like Fed so what do I know.
Regarding the serve, I think even if there isn't a persistent injury/niggle (we won't hear even if there is since he's not the cheat), I think Fed's game might be more affected by the confidence he has in his back. Is he willing to risk and go all out with the serve. He did mention 'playing with the breaks on' also talked about being able to go full out in his last training session before Monday so I hope all is well.