Officials admitted to USC coach Lincoln Riley after halftime that they made a mistake with the clock situation at the end of the first half.

USC was trying to set up a last-second score to close out the second quarter Saturday night against Arizona. After a first down, officials let the clock start before the ball was spotted and then ultimately expire before USC was able to get off a play.

The result was a scramble with only half the players on the field reacting as if the play was live and an incomplete pass from quarterback Caleb Williams that sent the game to halftime with a 17-13 margin.

“They admitted that they messed it up,” Riley said after the game. “My question was if you messed it up, why didn’t you just stop play and review it?

“The explanation given to me at the beginning of the third quarter was just that they obviously didn’t handle it properly, which, I mean, anybody knows that watching it.”

USC was trying to score points before the end of the first half and a 34-yard completion from Williams to wideout Brenden Rice put it in position to do so as the clock ticked under 10 seconds to play. With the ball at the Arizona 10-yard-line, USC appeared to have five or six seconds on the clock to try and spike the ball and set up another play.

Instead, the clock started running before the ball was set. An official stood over the ball, keeping USC from snapping it, and then moved the line of scrimmage back.

Williams got a snap and fired to a receiver downfield but the pass fell incomplete. After a brief conference between the on-field officiating crew, the half was ruled to be over.

Riley then tore into the crew before heading to the locker room.

It was a two-point game heading into the fourth quarter and it looked like points would be precious. The blunder at the end of the first half looked, at least for a bit, like it could loom large over the game.

But USC pulled away early in the fourth behind some brilliance from Williams. The Trojans got a pair of fourth-quarter touchdowns on back-to-back drives to go up 45-29.

Arizona got a late score to make the final line read 45-37, but it was ultimately toothless.