Jawann McClellan hit a three pointer to put the Wildcats up 71-67 wth 5:57 to play.
They would score four more points the rest of the way.
The Trojans scored five straight to take the lead, but Chase Budinger hit two free throws to put the Cats back on top.
It was their last lead. USC scored the next seven and the Trojans led 79-73 with 1:11 left. To make matters worse, Marcus Williams fouled out and Mustafa Shakur threw away a pass into the post and then quickly fouled Gabriel Pruitt, whose free throws ave two points of the mini-run.
Shakur answered with a quick lay-in and the Cats chose not to foul and wound up forcing a turnover.
The Cats were down four with just under :30 to play but were unable to get a good look in a timely manner. After running over 10 seconds off the clock Sahkur missed an off balanced shot. The Cats rebounded but took more time off the clock before getting another shot off. Buddinger missed a three from the corner and when the Cats finally fouled there were less than six seconds left in the game and it was effectively over.
In the end the turnovers doomed the Wildcats. The Cats coughed the ball up 16 times, a lot coming on lazy passes. Williams committed seven turnovers on his own, with Shakur losing the ball four times. USC only turned the ball over nine times.
Nick Young killed the Cats again. He scored 30 in Los Angeles, and pumped in 26 in the Tucson rematch. In fact the three Trojan perimeter players scored 69 of USC's 80 points with Loderick Stewart matching Young's 26, and Pruitt scoring 17.
Arizona shot 50% from the field, but it was not enough. Budinger led the Wildcats with 19. Shakur added 16 and six assists.