USC quarterback Matt Barkley stands in disbelief after Stanford recovered… (Wally Skalij / Los Angeles…)
USC, seeking to regain status as one of the top programs in college football, played No. 4 Stanford even.
The Trojans forced the high-powered Cardinal into triple overtime and appeared on the verge of sending the game into a fourth extra period.
That's when it all went bad for the Trojans.
Stanford linebacker AJ Tarpley recovered a fumble by USC running back Curtis McNeal in the end zone, sending the No. 20 Trojans to a 56-48 defeat before a stunned crowd of 93,607 Saturday night at the Coliseum.
"It hurts right now because we were so close," USC quarterback Matt Barkley said.
It was the second year in a row that USC lost to Stanford on the final play, the Trojans falling last season at Palo Alto on a last-second field goal.
On Saturday, Stanford increased the nation's best winning streak to 16 games, stayed in the race for the BCS national title, and improved to 8-0 overall and 6-0 in the Pacific 12 Conference.
USC fell to 6-2 and 3-2.
"No excuses," McNeal said. "I just fumbled."
The game was far different from the last time the Cardinal visited the Coliseum. In 2009, Stanford pummeled the Trojans, 55-21, sending former coach Pete Carroll to the worst loss in school history.
Regulation ended Saturday with the score tied, 34-34, sending USC into its first overtime game since a triple-overtime defeat at California in 2003.
USC Coach Lane Kiffin, however, believed that USC was denied a chance to win the game in regulation. With nine seconds left and the Trojans at the Cardinal 40, receiver Robert Woods caught a screen pass and ran toward the left sideline to try and get out of bounds. But officials ruled that he was tackled and that the clock had expired.
As the play was being reviewed, Kiffin said he was told that if they ruled Woods' knee was down inbounds and there was one second left, his team would have a timeout.
"Then they came back over and completely went against it," Kiffin said. "I'm extremely disappointed in that."
Stanford got the ball first at the 25-yard line in overtime and used seven plays to take a 41-34 lead on Jeremy Stewart's one-yard touchdown run.
The Trojans matched it with Barkley's 15-yard touchdown pass to Woods.
Stanford then opted to defend at the start of the second overtime and USC converted with a 12-yard touchdown pass from Barkley to tight end Randall Telfer for a 48-41 lead.
Stanford quarterback Andrew Luck tied it with an 11-yard touchdown pass to tight end Levine Toilolo.
The Cardinal then went ahead on Taylor's five-yard touchdown run and Luck's two-point conversion pass to tight end Coby Fleener, setting the stage for McNeal's miscue which was caused by tackle Terrence Stephens.
"That's what I like about this team," Stanford running back Stepfan Taylor said. "We're cool, calm, collected. We practiced for this during the week."
Luck, a Heisman Trophy front-runner, completed 29 of 40 passes for 325 yards and three touchdowns, with one interception that was returned for a touchdown by Trojans cornerback Nickell Robey late in the fourth quarter.
"For a couple seconds there I wanted to dig a hole and go bury myself," Luck said.
But in the end, the junior got the job done, driving the Cardinal to tie the score and helping his team win it with his play in overtime.
"This is what he lives for," Stanford Coach David Shaw said. "He lives for moments like this."
Barkley completed 28 of 45 passes for 284 yards and three touchdowns with one interception.
The fumble ruined a career night for McNeal, who rushed for a career-high 145 yards and scored two third-quarter touchdowns that gave the Trojans the lead.
"I think I was a little careless with the ball," McNeal said. ". . . At that moment, you have to hold onto the ball. Pretty much, I didn't take care of my job."
USC trailed 10-6 at halftime but came out in the second half seemingly energized and McNeal took over.
On the third play of the second half, he took a handoff from Barkley, ran off left tackle and then broke for the sideline, outracing Stanford's defense for a 61-yard touchdown that put the Trojans ahead, 13-10.
It was the first time Stanford trailed this season.
McNeal broke loose again on USC's next possession, scampering off the left side for a 25-yard touchdown and a 20-10 lead.
Stanford barely shrugged. Luck drove the Cardinal 85 yards and finished the march with a short touchdown pass to fullback Ryan Hewitt.
Then Luck drove Stanford to another touchdown, scoring it himself with a four-yard run on fourth and one to put the Cardinal back in front, 24-20.
USC came right back, Barkley hitting freshman receiver Marqise Lee for a 28-yard touchdown to regain the lead, 27-24.
Stanford tied the score on Eric Whitaker's 29-yard field goal with 5:10 left, but Robey put USC ahead when he jumped in front of receiver Chris Owusu, picked off Luck's pass and dashed 32 yards to the end zone for a 34-27 lead with a little more than three minutes left.
Luck didn't waver. He drove the Cardinal 76 yards in 10 plays, getting a huge assist from USC safety T.J. McDonald, who was called for a personal foul. Taylor finished the drive with a three-yard touchdown run to tie it with 38 seconds left.
Times staff writer Baxter Holmes contributed to this report.