Now we all know he's not going to go into Lord Goodell's office and say, "well yes sir I was faking the injury so we could get the play straight". Anybody who saw that play and watched the replay knows he needs acting lessons..LOL.
Big Ben was signaling for the trainers to come over before he was even on the ground yet.
Besides, leg cramps take more than just 1 play to get worked out. Usually they are on the sideline for at least a few plays, if not a series while they massage them out and give the player fluids.