BOULDER, Colo. (AP) Defensive tackle Delvon Simmons stuck out his big, right arm to show off the bruise from blocking a field goal.
Proud of that mark? ''Oh, yeah,'' he replied.
Simmons forced a fumble in addition to blocking a kick, Cody Kessler threw three touchdown passes in the second half and Southern California hung on to beat Colorado 27-24 on a frigid Friday night.
Trailing by two touchdowns in the first half to a 16-point underdog, the Trojans (7-3, 5-2 Pac-12) woke up on offense and scored 24 straight points. It was their 10th straight victory over Colorado (4-7, 1-6).
''I told them that in 21 years of football, I've never been more proud of a group,'' USC interim coach Clay Helton said. ''They'll never forget this moment, what we've been through this season. ... That's what is really cool - kids who refused to fail.''
Kessler gave the Trojans their first lead on a 2-yard pass to tight end Taylor McNamara late in the third quarter. The defense preserved the win by forcing a fourth-down incompletion on Colorado's final possession with 1:59 remaining.
''It was obviously not the start we wanted,'' said Kessler, who threw for 204 yards, three TDs and one interception. ''We were down going into halftime, but coach Helton came in and got the guys pumped up. We talked about it and figured out what we were going to do.''
Colorado turned to freshman quarterback Cade Apsay when Sefo Liufau left with a foot ailment in the second quarter. It was announced after the game that Liufau had a Lisfranc injury. He will need surgery and miss six-to-eight months.
''I feel bad for Sefo,'' Colorado coach Mike MacIntyre said. ''It's a tough deal.''
Apsay finished with 128 yards and two TD passes, including one to senior Nelson Spruce. This was Spruce's 22nd scoring catch of his career, tying him with Scotty McKnight for most in school history.
This wasn't the script Spruce envisioned in his final game at Folsom Field.
''It was right there, but it's kind of been the story of the season,'' Spruce said. ''We just weren't able to finish.''
Seemingly in control at 27-17 in the fourth quarter, USC surrendered a 45-yard punt return from Spruce to set the Buffaloes up the near the goal line. Apsay connected with George Frazier for a 1-yard score, which energized the crowd.
But Southern Cal's defense rose to the occasion. The Trojans finished with six sacks and forced a Christian Powell fumble that set up Kessler's strike to McNamara.
Simmons preserved the USC lead early in the fourth quarter when he got around the edge and blocked Diego Gonzalez's 51-yard field goal attempt. Adoree' Jackson scooped it up and raced 16 yards to the Colorado 36.
''What a huge play in the game,'' Helton said. ''What a huge play.''
Because on the next play, Kessler hit JuJu Smith-Schuster for a TD. Turned out to be valuable insurance.
At kickoff, the temperature was 41 degrees and dropped into the mid-30s by the second half. Not exactly SoCal sort of weather. The Trojans are now 12-8-1 in cold conditions, which the school defines as anything that significantly impacts a contest.
USC has dominated this series since Colorado entered the conference in 2011, outscoring the Buffaloes by a 195-80 margin entering the game. But this one was much closer.
Phillip Lindsay scored on a 4-yard run midway through the first quarter to give Colorado a 7-3 advantage. That was significant because it was the first time the Buffs have had a lead in a game against USC since Nov. 4, 2011.
It was the final home game for Larry Zimmer, the voice of Colorado football for 42 seasons. Zimmer was presented with a framed jersey after the first quarter on what happened to be his 80th birthday.
''The 42 years as I look back on it isn't as amazing to me as that at 80 years old, I'm still doing it,'' Zimmer said.
AP college football: www.collegefootball.ap.org
This story has been changed to reflect that officials are now crediting Delvon Simmons with blocked field goal.