LOS ANGELES (AP) -- All this talk about Joe McKnight, and very little action.
That finally changed in the fourth quarter of the highly regarded freshman's sixth game for Southern California.
McKnight, who prompted comparisons to Reggie Bush with his shifty moves and speed at John Curtis High in River Ridge, La., set up the game's final 10 points with a 45-yard punt return and 59-yard run Saturday, igniting No. 10 USC to a 20-13 victory over Arizona.
"To get a good win and finish it strong at the end was really cool," USC coach Pete Carroll said. "We're very fortunate."
Mark Sanchez, a third-year sophomore making his first start, threw a 25-yard scoring pass to Fred Davis with 10:47 remaining on the first play after McKnight electrified the Los Angeles Coliseum crowd of 84,671 with his punt return.
Suddenly, the Trojans led 17-13. Their defense would hold the Wildcats without a first down after that.
"The seniors were on the sideline, everybody's on the sideline saying we just need a play just to get everybody up," McKnight said. "I really haven't been proving to people what I can do, so I hope I prove it to them now and I prove to the seniors that I can play with them."
McKnight's 59-yard run set up David Buehler's 23-yard field goal with 57 seconds left that completed the scoring.
"Joe McKnight, you saw him finally, you saw what we've been talking about," Carroll said. "He's a fantastic football player. It just hasn't happened for him yet. It's just a confidence deal, it's just getting out there.
"He's not totally over the hump yet. He's not quite there yet. He has so much stuff to him. He's so fast, he's so quick, he's so elusive. He's going to continue to make big plays."
McKnight acknowledged he's had problems holding onto the ball.
"But I told coach Mac I'll never drop it again," he said, referring to running backs coach Todd McNair. "That's the only thing I was worrying about, keeping it high and tight and close to my body."
The game was USC's first since a shocking 24-23 loss to 41-point underdog Stanford, snapping the Trojans' 35-game winning streak at home. It appeared they were going to go down again, this time as 21-point favorites, before McKnight's first big play. A punt hadn't been returned for more than 12 yards against Arizona punter Keenyn Crier previously this season.
Crier's 83-yard punt, one yard shy of the school record set in 1930, rolled dead at the Trojans' 1 with 7:09 remaining. After USC picked up a first down, McKnight broke loose, racing to the Arizona 27.
Sanchez later scrambled for 10 yards to the Arizona 2 on a third-and-7 play, and Buehler kicked his second field goal three plays later.
USC (5-1, 3-1 Pac-10) won despite being held to 12 total yards in the second quarter and 50 in the third period.
"It was ugly, it was a little bloody, it was a mess for a while there," Sanchez said. "I just couldn't lose this game, we couldn't lose this game. We weren't going to let it happen."
The Wildcats (2-5, 1-3) were clearly the better team until McKnight's punt return, having overcome a 10-0 deficit to take a 13-10 lead.
"Tough loss," Arizona coach Mike Stoops said. "I thought we had a great opportunity and we let it slip away. We just missed out on some opportunities. Our defense played its best game of the season."
Sanchez, who entered having thrown 10 college passes, completed 19 of 31 for 130 yards with two interceptions. He was filling in for John David Booty, who broke the middle finger on his throwing hand against Stanford.
Booty's status for next weekend, when the Trojans travel to play Notre Dame, is uncertain.
McKnight finished with a career-best 75 yards on 13 carries. He returned two punts for 15 yards and rushed for 79 yards on 16 carries in his first five games at for the Trojans.
Arizona's Willie Tuitama completed 30 of 43 for 233 yards. The Wildcats were held to 22 yards rushing.
"I can honestly say we left nothing on the field," Tuitama said. "Our defense did a great job of containing them for almost the entire game."
Jason Bondzio kicked a career-long 45-yard field goal early in the third quarter, giving the Wildcats their 13-10 lead. Neither team would threaten to score again until the final period.
The Trojans moved 85 yards on 10 plays the second time they had the ball, scoring on an 18-yard run by Chauncey Washington for a 7-0 lead.
Tuitama completed 10 passes for 67 yards before throwing his first incompletion late in the first quarter, but the Wildcats lost a fumble and punted twice in the period.
Sedrick Ellis recovered Nic Grigsby's fumble at the Arizona 31 early in the second period, setting up a 27-yard field goal by Buehler to make it 10-0.
The rest of the quarter belonged to Arizona.
First, the Wildcats moved 74 yards on eight plays, scoring on a 1-yard run sneak by Tuitama, who completed 4-of-4 passes for 67 yards on the drive.
Then, three plays after Antoine Cason's 13th career interception and 27-yard return to the USC 19, Bondzio kicked a 28-yard field goal to make it 10-all.
Corey Hall intercepted another pass by Sanchez following the kickoff, but fumbled at the end of a 17-yard return and Matt Spanos recovered.
Already playing with a makeshift offensive line, the Trojans lost left tackle Sam Baker in the second quarter with an injured hamstring. Leading rusher Stafon Johnson missed his second straight game due to a sprained left foot.