Notre Dame is heading to the College Football Playoff for the first time.

OK, we’re not going to know until Dec. 2 that Notre Dame is officially in the playoff field, but it’s all but certain that the Irish will be a part of the four-team field after a 24-17 win at USC on Saturday night. Notre Dame is one of just three Power Five teams, along with Alabama and Clemson, to finish the regular season undefeated.

It was not the prettiest of wins, but all the Irish needed was a win. Notre Dame’s defense buckled down after USC jumped out to a 10-0 lead as the Irish scored 24 unanswered points.

The 10-point deficit was the largest that Notre Dame had faced all season. It didn’t blink. The Irish pulled within three on a 24-yard touchdown pass from Book to Chris Finke in the second quarter and took the lead when Dexter Williams burst through the line for a 52-yard touchdown run in the third. That was more than enough as the promise that USC showed early in the game disappeared.

USC pulled within a touchdown with 46 seconds left but Notre Dame recovered the onside kick.

Ian Book throws for 352 yards

Book didn’t have his best game. There were a couple of throws that he missed and he had an ill-advised interception in the second half. But the quarterback was 22-of-39 for 352 yards and also threw two touchdowns.

The 352 passing yards are the most Book’s tallied so far this season. Since he was inserted into the starting lineup after Week 2, Notre Dame’s offense has thrived.

The addition of Williams has been key too. He didn’t play in any of Notre Dame’s first four games and had 21 carries for 161 yards and a score in his first game of the season. His touchdown run Saturday night meant that Williams scored at least one touchdown in seven of the eight games he played in. Notre Dame’s close win against Pitt was the only game where he was held scoreless.

The heat grows on Clay Helton

The loss means USC finishes the season at 5-7. It’s the Trojans’ worst record since 2000, the last year of Paul Hackett’s tenure before the school hired Pete Carroll.

Helton was booed by fans when he appeared on the Los Angeles Coliseum video screens early in the game and a plane flew overhead before the game with a banner that asked athletic director Lynn Swann to fire him.

Will Swann make the move? Helton was just signed to a contract extension after an 11-3 season in 2017. But the Trojans regressed significantly in 2018. He told media after the game that he would be talking with Helton “soon.”

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Nick Bromberg is a writer for Yahoo Sports.

Follow @NickBromberg on Twitter

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