"I hope I'm wrong with this assessment but, unless the Spurs can somehow get another quality effective athletic big (6'10" or taller), I'm not convinced that will change. For...all the specialty qualities that McDyess, Blair and Bonner bring to the team...none of them seem to be able to solidify the post while Duncan is out."
You have hit the nail on the head. Our back court will be fine as long as Tony gets everyone involved. The offense is not the problem. It is the defense. Spurs defense has been built over the years by crowding the shooters (this is why Bowen was so effective) and driving them into the bigs for blocked or altered shots. Our unathletic or short bigs are having a hard time getting into position.
The perimeter defense drives the shooter into the lane.
The shooter is met by the interior defender.
The shooter then passes to the open man as the second big does not rotate fast enough or is not big enough to alter the shot in the first place.
So, the perimeter defender has to give some space to prevent the drive thus leaving the opposing team with more open shots than ever before.
Many complain that the perimeter defense is the problem, but this is predicated on the failure of the bigs to alter shots in the defensive scheme that we use.