I wouldn't be so sure.
He took a tough helmet to helmet hit in the GB game near the goal line. He looked like he got his bell rung, but jumped back up like nothing happened.
Also, his last run in the Detroit game (trying to get 10 more yards), he took a really hard hit on the lower leg while running out of bounds.
That was scary !
A little lower and that hit would have been right on the knee !