The story: After finding itself in an unfamiliar deficit heading into the fourth quarter, USC charged back against Ohio State in an emotional 18-15 win that came down to the final seconds.

Down 15-10 and 86 yards from the goal line, the Matt Barkley-led Trojan offense completed a 14-play drive, culminating in a two-yard Stafon Johnson touchdown run in the final minutes of the fourth quarter.

Ear-splitter · The 106,033 fans in attendance at Ohio Stadium (a new Ohio State record) reportedly made Matt Barkley’s ears ring. - Leah Thompson | Daily Trojan

Barkley, a true freshman, kept his composure on the decisive drive, completing three of five passes for 55 yards. Some of his best plays came when he got the ball into junior running back Joe McKnight’s hands. McKnight rushed for 30 yards on five carries during the drive and also caught a 21-yard pass.

Once near the goal line, Johnson relieved McKnight, taking a handoff and sprinting to the right corner of the endzone, where he high-stepped in untouched for the go-ahead score. USC converted the two-point conversion on a Barkley pass to McKnight to take the lead for good.

The game-winning drive provided the Trojans’ only points of the second half.

Ohio State dominated the field position battle, beginning three second-half drives in USC territory. The Trojan defense kept USC in the game, stymying the Buckeyes and allowing them only three second-half points.

Play that changed the game: Barkley’s 21-yard pass to McKnight.

Barkley’s pass came on the third play of its game-winning drive. Barkley was sacked on the first play and a false start penalty took the Trojans back. After a McKnight run, the Trojans were faced with a 3rd down and eight from their own 16-yard line and appeared to be in trouble.

Barkley dropped back to pass and found an open McKnight a few yards past the line of scrimmage. McKnight beat an Ohio State linebacker to the inside on an option route and sprinted up the field after he caught Barkley’s pass.

The pass gave USC’s offense much-needed breathing room as well as game-altering momentum. Everything seemed to start clicking as the Trojans put together their longest scoring drive of the game by far.

Most valuable player: Matt Barkley.

Although the youngster’s numbers weren’t amazing — 15 of 31, 195 yards, one interception and no touchdowns — the poise with which he carried himself on USC’s final drive could not be captured in the stat sheet.

The roaring Ohio State crowd didn’t seem to faze him. Neither did the interception he threw in the first half to the Buckeyes’ Ross Homan. His teammates said his demeanor remained the same throughout the entire game.

“Matt was the same person the whole game,” McKnight said. “[He] never lost his composure, [he] just kept coming in the huddle and calling plays.”

Coach Pete Carroll was impressed as usual with his 19-year-old sensation.

“It’s just remarkable that he can show all that so early,” Carroll said. “But he showed also that he can take you and win in the fourth quarter, which is huge.”

Stat of the game: 106,033.

The number of fans on hand at “The Horseshoe,” a new attendance record for Ohio Stadium. The jam-packed crowd hardly sat down the entire night and was at its loudest when the game was on the line.

“It was 100 guys versus everyone in the world it seemed like,” Carroll said.

But the Trojans remained unfazed despite the noise.

“It was pretty loud, not gonna lie,” Barkley said. “I think my ears are still ringing a little bit. But I mean we played through it. The actual noise didn’t affect how we were going to play.”

Quote of the game: “The questions that everybody has been asking about Matt [are] legitimate… All we can tell you is the guy’s really special. He’s into it, he’s having fun, he’s not arrogant, he’s not cocky — he’s just a complete ball player.”

— Carroll about Barkley’s ability to handle big-game situations.

On track into the Pac: After surviving their biggest non-conference test of the season, the Trojans are in prime shape entering their Pac-10 schedule, which starts next week at Washington.

But seeing as their only loss in 2008 came against conference opponent Oregon State — the game following the Ohio State matchup ­— Carroll said he already warned his team to not get caught up in the celebration and overlook the Huskies.

“I already addressed it,” Carroll said. “This game can’t carry into the next week. This game’s over. I told them, ‘It’s already on ESPN, they already showed the highlights to everybody, so that’ll be over by the time we get home.’”