Dirk's right ankle is done after half-time, he can't explode to the right, that's when putting Timmy on him may not be as costly. Then the Spurs can play either Nazr or Rasho on Dallas's centers without there being 'switching difficulties'. Also, there is no need to double Dirk in the middle from the right side. If he goes right, he's only gonna take one step and pull up and shoot or pass, too quick for the trapping defenders to do any good, and it leaves a man open.
Also, if the Spurs swing the ball to the left, then swing it to the right, and have Manu play on the right-side (Dirk's side on D), instead of the left, that lane is gonna be open all-night long, because Dirk just has no explosiveness on his right leg. This is what led to the tremendous Finley dunk, and I was surprised more Spurs haven't taken advantage of it. The only thing I can surmise is that the Spurs haven't noticed this trend on game film yet.