Illegal Screen?

[stiffler3492]

Try and stay with me on this one. It might be hard to envision.

Team A has a fast break, and A1 has the ball coming down the right side of the floor. A2 is running right with A1, and on the same side of the floor, but closer to the middle of the floor.

B1 is coming down the middle of the floor trying to catch up with A1. A2 then moves into B1's path and faces the basket. He sticks his rear end out and kind of looks for B1 to make sure he contacts B1. He does, and I wave off the layup and call an illegal screen.

I called it not because A2 didn't give B1 time and distance to avoid it, but because of the way he was standing when contact was made (with his butt out). Ever seen this play, or did I get it wrong?