Patty O for sure, he has the biggest shoes to fill at the moment as our backup center, none of these other new guys (Walker, Giddens/Miles, etc.) will need to play a huge role, and I know already what to expect and hope for from TA.
Miles might look good tonight, but for a guy with his injury history he's playing on borrowed time, so "how good he looks tonight"--which I think will be very good--isn't really the point.
Long term however, Walker by a mile, biggest potential to be a true impact player from this off season.