No matter how much information you have at your disposal, the performance of some players will be extremely difficult to predict, regardless of injuries. No one could have predicted how bad Crawford would be in 2011, and no one can exactly explain it, either.
Some guys are just extremely erratic - like Buchholz and Masterson - and no one is sure exactly why.
Some guys 'lose it' and then get it back, like Lester - possibly because of an adjustment in mechanics.
I would love to see someone here try to predict the final 2015 numbers for our current rotation. If your numbers are way off because of injury, you get a complete pass, of course.