Senior running back Dexter Williams dashed for the go-ahead touchdown and junior quarterback Ian Book passed for two scores as third-ranked Notre Dame completed an undefeated regular season with a 24-17 victory over host Southern California on Saturday night at the Los Angeles Memorial Coliseum.

Williams totaled 151 yards (97 rushing, 54 receiving) and junior running back Tony Jones Jr. scored on a 51-yard pass play as the Fighting Irish (12-0) undoubtedly clinched a spot in the four-team College Football Playoff.

Book completed 22 of 39 passes for 352 yards as Notre Dame recovered from a 10-point second-quarter deficit.

"Today was gritty, it wasn't perfect. Give a lot of credit to USC," Notre Dame coach Brian Kelly said in a postgame interview with ABC. "... Our kids finished the season perfect. It's hard to do that."

Freshman quarterback JT Daniels completed a school-record 37 passes while throwing for 349 yards and one touchdown on 51 attempts as the Trojans (5-7) lost for the fifth time in six games.

Sophomore receiver Tyler Vaughns caught 12 passes for 120 yards and one touchdown.

USC finished with its first losing season since 2000, which increases speculation over whether coach Clay Helton will be retained. Paul Hackett was fired after the 2000 season for having a 5-7 mark.

The Fighting Irish took their first lead when Williams exploded on a 52-yard scoring run. He lined up to the right of Book, took the handoff and darted to the left, quickly breaking into the clear and outrunning the secondary to give Notre Dame a 14-10 advantage with 10:55 left in the third quarter.

The Irish increased their lead to 17-10 when senior Justin Yoon's 46-yard field goal narrowly cleared the crossbar with 1:07 left in the third. The field goal was Yoon's school-best 58th, breaking a tie with Kyle Brindza (2011-14).

With little more than three minutes remaining in the fourth, USC came with an all-out blitz on third-and-5 and Book tossed the ball to Jones in the left flat. Jones galloped up the left sideline and received a downfield block from senior wideout Miles Boykin while completing the 51-yard score to increase the margin to 14.

Daniels threw a 20-yard scoring pass to Vaughns with 48 seconds left, but Boykin recovered the ensuing onside kick to seal it.

Daniels was 26 of 31 for 244 yards in the first half as the Trojans held a 10-7 lead.

USC opened up a 10-0 lead in the first 18-plus minutes on sophomore Vavae Malepeai's 14-yard scoring run and sophomore Michael Brown's 30-yard field goal.

Notre Dame finally got on the board with 2:20 left in the half when Book tossed a 24-yard scoring pass to senior receiver Chris Finke.

--Field Level Media