Originally Posted by JamStone
That's an incorrect statement.
The semi-circle does not only apply to the primary defender. The majority of the time, it is a secondary or help defender that it applies to when an offensive player drives the lane.
Where the semi-circle does not matter is if it is not a "penetration / driving move" to the basket. For example, if Ben was making a post move, and lowered his shoulder into Nazr, even if Nazr was in the semi-circle, it could be called an offensive foul.
On this particular play, Ben Wallace was driving towards the basket on the baseline. The semi-circle was definitely applicable to that play, and Nazr was in the semi-circle where at the very least a non-call should have been made.
At the end of the day, it doesn't matter because the Spurs beat the Pistons by 15 and it wasn't that one play that made the difference in the game. But, let's not miscontstrue the rules of the game. That was not an offensive foul. It was a bad call.