Even if other bigs leave Duncan by himself to jump at Amare or whoever, it won't make much of a difference IMO. Duncan is that good defensively. Just his presence down low makes a lot of our players change their shots. Plus you can't forget he never gets fouls called against him.
The Spurs also rotate better than any other team in the league. There seems to always be someone there to help out. Like I said, they might get other teams to fall into this trap, but the Spurs, being our biggest hurdle, could still easily find ways to adapt.