By ANTONIO GONZALEZ
AP Sports Writer
STANFORD, Calif. (AP) - Matt Barkley's Heisman Trophy credentials are no longer perfect and neither is Southern California's national title resume.
Once again, Stanford is the reason.
Barkley threw for 254 yards and two interceptions while USC rushed for only 26 yards, and the second-ranked Trojans fell to No. 21 Stanford 21-14 for their fourth straight loss in this series.
"You learn and go back to playing Trojan football," said a disappointed Barkley, who has beaten every conference teams but Stanford. "We got to just not put the blame on anybody, learn from our mistakes and make sure we bounce back."
Barkley completed only 20 of 41 passes. He was sacked twice on the final drive for the Trojans (2-1, 0-1 Pac-12) and threw out of bounds on last, desperate heave on fourth-and-39 from USC's 25-yard line.
Coming out of a two-year bowl ban, USC had national title dreams. Now the Trojans, who were held scoreless for the final 41:19, will have to climb out of another hole to get there.
"It's not the end of the world," said USC coach Lane Kiffin said, now 0-3 against Stanford. "We'll get back on the plane, go home and we'll get better."
Josh Nunes threw the go-ahead 37-yard touchdown to Zach Ertz early in the fourth quarter, and Stepfan Taylor ran for 153 yards and scored two touchdowns for the Cardinal.
Once the clock hit zeros, a sold-out crowd of 50,360 at Stanford Stadium rushed the field, tossing streamers and jumping in a wild celebration at midfield with Cardinal coach David Shaw and his players caught in the middle of the mess. Stanford (3-0, 1-0) is 3-0 for the third straight season for the first time since 1970-72 and has its longest winning streak ever against USC in a rivalry that dates back to 1905.
"I love the energy and I love the enthusiasm," Shaw said. "But we are not surprised."
He might be the only one.
Luck, the No. 1 overall pick by the Indianapolis Colts, two-time Heisman Trophy runner-up and perhaps the greatest player in school history, is gone and so much about this season seemed uncertain. Now the only chance another senior quarterback and possible No. 1 overall pick has for revenge against the Cardinal is a rematch in the Pac-12 title game.
Stanford's Jordan Williamson missed field goals of 47 and 23 yards and had a 51-yarder blocked by T.J. McDonald. With a defense that flustered Barkley and a new quarterback that found his footing late, the kicker who missed three field goals in the Fiesta Bowl loss to Oklahoma state last season could smile in the pile with everybody else.
Except for the Trojans, that is.
A year after Luck led Stanford back in a 56-48 triple-overtime thriller at the Coliseum, a new crop of Cardinal players delivered another moment to savor.
Taylor took a short screen pass and scurried 23 yards for a tying touchdown late in the third quarter. Nunes scampered 12 yards on a third-and-10 from midfield in the fourth and then delivered the strike to Ertz, who juked a defender and dove into the end zone to give Stanford a 21-14 lead and send the home fans into a flurry with 10:20 to play.
"That was a great route," Nunes said. "We knew we had been trying to set up that route for a while, and Zach just ran a great route with great protection."
The last chance for USC never amounted to much.
Marqise Lee caught an 18-yard pass on fourth-and-4 on the sideline that was originally ruled out of bounds. After a video replay, officials ruled Lee's left foot landed in bounds and he controlled the ball.
Mistakes finally doomed the Trojans.
USC had a 10-yard holding penalty, then Trent Murphy sacked Barkley, followed by a 5-yard false start penalty on the Trojans and a sack by Chase Thomas before Barkley's final heave out of bounds.
Nunes threw for 215 yards, two touchdowns and two interceptions on 15-for-32 passing in the redshirt junior's biggest game yet. In the end, all that really mattered to Luck's replacement was the win.
USC center Khaled Holmes, who left last week's victory over Syracuse on a cart with a right leg injury, struggled in his limited time on the field along with the rest of the offensive line to protect Barkley from Stanford's relentless rush.
Stanford sacked Barkley four times and had him constantly losing his poise in the pocket. The Cardinal outgained the Trojans 417 to 280 total yards and held USC to only 26 yards rushing.