the first year he had 1 concussion, had the LCL injury where he missed one game and than was playing hobbled the next few games. It was obvious he shouldn't be playing than tears his acl in the playoffs and that was pretty much it. It ruined his entire career.
He did go back in the game for 1 play without doctors permission, but than was pulled immediately after that. Being a Ravens fan you should remember this was on the final drive of the game. The TD put the skins in OT and then they won the toss and had a long kickoff return that put them right into fg range.