Well first of all Cigano also had a knee injury, so both of them were not in their 100%.
Secondly I think that the injuries had nothing to do with the result. Cigano punches very hard, and he connected a very huge punch to Cain's ear. Then he finished him with GnP.
The fight lasted only 1 minute, and most certainly this time it is going to last longer. However injuries can not denie the fact that JDS is a much better striker than Cain, just as Cain is a better wrestler than Junior. (However we do not know how much better he is, we have not seen JDS on the ground yet)