Vince Ellis of the Detroit Free Press reports:

Villanueva suffered a broken nose with 9:30 left when he was fouled by the Hawks’ Zaza Pachulia on a drive to the basket. As he was falling his face appeared to hit near the hip of teammate Ben Wallace.

His nose started bleeding profusely and a time-out was taken. Pistons personnel was able to slow the bleeding just enough so Villanueva could make the two free throws. He then went to the locker room and never returned.