PASADENA, Calif. -- USC coach Clay Helton took a seat on the back of a golf cart, exhaled deeply and looked at his star quarterback, Sam Darnold: “Come on, one-four, let’s go home,” he said.

Just three months earlier, Helton was widely viewed as a first-year flop, and Darnold was an anonymous backup who wore jersey No. 14.

On Monday night, however, they were escorted into the tunnel and out of what was then a mostly empty Rose Bowl after having just won one of the most memorable contests in the bowl’s 103-game history.

USC’s 52-49 victory over Penn State in the Rose Bowl Game presented by Northwestern Mutual will be remembered for a number of reasons, but it might go down as the day Darnold broke through as a national star -- if he wasn’t already.

Since reversing the course of the Trojans’ season after being inserted as the starter in their fourth game, Darnold has been among the best quarterbacks in the country. It’s one thing, however, to play at that level against mostly average Pac-12 teams for a Trojans team that had been largely written off. It’s another thing altogether to throw for 453 yards and five touchdowns and engineer an 80-yard game-tying drive with under two minutes to play in The Granddaddy of Them All.

Darnold’s 473 total yards broke the Rose Bowl record of 467, which was set by Vince Young during the Texas quarterback's all-time great performance against USC in 2006.

“I love the quiet confidence about him,” Helton said of his redshirt freshman quarterback. “You never saw his demeanor change tonight. Whether he was throwing a touchdown or whether we got stopped on offense, you just never saw his demeanor change.

“He was so glued in and so focused at the task at hand. It was just so fun as a coach tonight to watch so many great players on the field perform.”

For much of the second half, though, it couldn’t have been much fun for Helton.

The Trojans jumped out to a 13-0 lead but watched Penn State score touchdowns on seven straight possessions, including on three consecutive offensive plays to open the second half. In the third quarter, USC lost its leading tackler, Cam Smith, to a targeting ejection and do-everything cornerback Adoree’ Jackson to injury.

When they trailed 49-35 early in the fourth quarter, the Trojans’ chances at winning seemed bleak, and a number of questionable decisions by the ACC officiating crew didn’t help. There was one decision, however, that went for USC, and it provided a clear turning point in the game.

Darnold found junior receiver JuJu Smith-Schuster down the right sideline for 27 yards with 8:28 remaining, but at first, the pass was ruled to be incomplete. And really, it was hard to blame the official. Few players in the country have the ability to make that catch and get a foot down, but there’s a reason why Smith-Schuster is viewed by many as a potential first-round NFL draft pick.

After a review, USC was awarded the ball at the Penn State 3-yard line, and Ronald Jones II, who wore No. 4 in the game to honor the late former Trojans running back Joe McKnight, ran into the end zone on the next play to bring USC to within one score of catching Penn State.

The teams traded punts before USC’s defense needed to make a stand to keep its hopes alive. Penn State took over at its own 25 with 3:56 left and picked up one first down. But on third-and-4, USC linebacker Michael Hutchings, a senior captain who played sparingly until this season, tackled star running back Saquon Barkley for a loss of 7 yards, forcing Penn State to punt.

With 1:59 remaining and the ball at their own 20, the stage was set for the Trojans. Five plays and just 32 seconds of game clock later, Darnold hit sophomore Deontay Burnett for the game-tying score.

“So what Tay's actually supposed to do is keep a straight line, not necessarily run a post like that,” Darnold said of the touchdown catch. “But just the player that he is, he made a play, and I saw him.”

Burnett, who began the year as a backup, finished the Rose Bowl with 13 catches for 164 yards and three touchdowns.

With 1:20 left, there was still time for two more USC players to etch their names into Rose Bowl lore.

Penn State wasn’t content to play for overtime. Understandably, coach James Franklin wanted to go for the win in regulation, but that meant the Nittany Lions would have to take shots down the field -- as they had done all season.

This time, it proved costly.

After letting one sure interception go through his hands, USC safety Leon McQuay redeemed himself with the biggest play of his career. He picked off a Trace McSorley pass and returned it 32 yards to the Penn State 33 with 27 seconds left.

USC place-kicker Matt Boermeester had missed two field goals earlier in the game, but the coaching staff had faith. On the headsets, the coaching staff discussed the situation and determined they already were in Boermeester’s range. From there, it was just a matter of setting him up with the proper angle.

Jones rushed for 5 yards, Darnold followed with a spike of the ball to stop the clock and out trotted the son of a former UCLA kicker to win the Rose Bowl for USC. As soon as he kicked it, Boermeester knew it was going in and took off for the opposite end zone in celebration.

It was USC’s record 25th Rose Bowl victory and won’t soon be forgotten.