Frankly, outside of getting 4 or 5 TDs, Havner wasn't all that great.
Yes he plays some LB, but if you need him to do so then you are pretty screwed seeing as you've lost not only your starters but at least a couple of your back-ups too.
Also, he does not block particularly well. I still remember a play last year, where HAver missed a block and Rodgers got nailed going out of bounds. He gets up, has words for Havner, and Havner in return begins yelling at A-Rod.
Frankly, I think Havner's snaps could go to a more talented (but raw) Quarless. He'd be instantly a more credible threat, assuming that he can catch can the ball.
The NFL: Where Greg Jennings Happens.