Someone in the national media said it (I can't recall whom), I was also thinking it, and I believe we saw it last night: The advantage of Lewis over Lienart is his athleticism and ability to move/run. They're about equal in passing ability (and neither one was that good), but with the state of this team, and the lack of time to learn the full offense, the new backup QB who can run and make things happen with his feet is more valuable than the immobile one.
It has to be Lewis.