Arizona's Jared Baker would not be denied the end zone all three of his touchdowns in the second half.
Baker's third touchdown with just over a minute left in the fourth quarter had the Wildcats trailing by two.
Then Arizona recovered the on side kick.
Wildcat kicker Casey Skowron had a chance to win the game with a 36 yard field goal. It was wide right.
"God’s got a plan, and we’re not exactly sure what his plan is for us yet but he is testing our will, leadership and character." USC head coach Steve Sarkisian said. "I couldn't be more proud of our team, just to continue to fight."
"Losing on the last play is not easy. "Arizona head coach Rich Rodriguez said. "We just didn't make a play at the end to win it."
Southern California should give it's game ball to running back Javorius Allen who rushed for 205 yards and three touchdowns.
Allen's third touchdown, a one yard run late in the third quarter to give the Trojans a 28-13 lead proved to be the game winner.
Arizona quarterback Anu Solomon put up some big numbers. Soloman attempted 72 passes vs Southern California, completed 43 of his throws for 395 yards and a touchdown.
"Anu Solomon competed well." Rodriguez said. "Everyone says he struggles and doesn't make every play, but we put a lot on the guy. He didn't make all the big plays in the first half, but for a redshirt freshman playing in a big arena, Solomon has accounted for himself pretty well."