Why is the Spurs’ pick-and-roll effective?

It is no secret — with guards Manu Ginobili and Tony Parker being asked to handle more than a fourth of the possessions, respectively — that the Spurs’ offense revolves around the pick-and-roll exploits of their two All-Stars.
An effective yet simplistic way of creating good looks from a pick-and-roll is to use “drag” action to exploit opposing defenses, especially in transition. The standards for the set still apply but because the defense is occasionally caught in poor position, the set is generally more effective.
Brett Koremenos, in a piece describing the five signature plays of the quintet of title contenders, explained the effectiveness of the drag action that is prevalent in Gregg Popovich’s arsenal.
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For instance, in the above video, Tim Duncan sets a screen in transition designed to prevent a hedge, as Kendrick Perkins has yet to recover, and simultaneously free up Parker from Russell Westbrook. The screen dislodges an unsuspecting Westbrook and since Perkins isn’t really in the picture, Parker releases unimpeded for a foul line jumper, a distance in which he made 45.2 percent of his shots last season (and likely higher if left open).
These kinds of sets aren’t really intricate sets but they are still efficient in transition, where scoring points is much easier. Expect the Spurs to continue running pick-and-rolls at a league-high rate and, most importantly, generating good looks against the opposition.