The expectations are going to be fair for a guy who will be 10th on the roster.
If he can
1) set a screen where in he actually impedes the progress of the defender
2) grabs a rebound and " crashes the boards"
He's already better than Blair and Bonner.
He's going to be good reinforcement and depth against the Grizzlies and Clippers by virtue of not being 6'8 and being attributed as physical.
Against quicker teams that bother the spurs he may not be needed. But he definitely gives the spurs and added dimension they have not had in 4 or more years, another back up 6'11 banger