That doesn't make sense on so many different levels.
The main point about Manu is he can't physically handle playing more than 30 minutes per game. He's not injured right now by his own admission ... he's worn out. If you don't think that three game stretch had anything to do with it, then you must not be following Manu very closely.
On the court, you can see him getting tired if he plays over 30 minutes. In the Nets game, he asked out of the game after THREE minutes in the second half because he was tired. Him being tired has to do with how many minutes he's playing. This is basic stuff.
Manu isn't a super hero. He gets tired because he plays so damn hard. I don't think any player plays as hard as he does. He's not going to change (as he said in an interview recently), so the Spurs are going to have to limit his minutes so he doesn't get as tired.
In future seasons, the best way to utilize him would be off the bench ... unless you want him playing 12 of his 28 minutes in the first six minutes of each half.