ITB Fun Fact Trivia Question

I was running through my usual message boards trying to find something to write about and I came across a good trivia question. Again, you can probably get the answer pretty easy if you google it, but try to get it on your own. Post your answer in the comments section. Question: Who did Peyton Manning take over the starting quarterback job from at Tennessee? Hint: This player is still active and is expected to start in Denver Monday night, although not at quarterback.