If a person has a sprained MCL how much pain would he be in?

I just read on nfl.com that the Chicago Bears are saying Jay Cutler has a sprained MCL and that's the reason he left the game in the 2nd half on Sunday. But he was on the exercise bike for a while and he walked up and down the sidelines without any noticeable limp. I think he faked the injury. What do you think?