LOS ANGELES (AP) Southern California head coach Clay Helton walked up to quarterback JT Daniels, looking into his eyes for confirmation the second freshman to start a season opener in the program's storied history was not overwhelmed by the moment.

''They're either that big,'' said Helton, holding his hands wide open, ''or they're like, `All right, let's roll.' "

Daniels was ready, throwing for 282 yards with a 43-yard touchdown pass to Amon-Ra St. Brown to help the No. 15 Trojans overcome a sluggish performance and defeat UNLV 43-21 on Saturday.

Outside of an early gaffe where Daniels turned the wrong way trying to hand the ball off to running back Stephen Carr, forcing the 2017 Gatorade national player of the year to scramble for a 5-yard gain, there were no apparent nerves from the 18-year-old.

Daniels did admit to feeling goosebumps coming down the tunnel for the first time before joining Matt Barkley in 2009 to start in his USC debut.

''It's hard to put in words what it's like to run out there and hear everybody cheering for you and rooting you on. For my first time in the Coliseum, it was really magical,'' said Daniels, who was 22 of 35 passing.

Daniels began to find a rhythm on his third drive with three consecutive completions to fellow freshman St. Brown. The former Mater Dei High School teammates connected for their first college touchdown on the first play of the fourth quarter, with St. Brown getting a step behind cornerback Jericho Flowers on a post route to give USC a two-possession lead.

''I don't care if you're a four- or five-star guy, I don't care if you're the No. 1 guy in the country. You walk into a place like SC, you get named the starter, you gotta go into the Coliseum and win a football game, that's tough for any kid,'' UNLV coach Tony Sanchez said. ''Overall, I respect the heck out of him and thought he did a good job.''

St. Brown had seven receptions for 98 yards, Aca'Cedric Ware rushed for 100 yards and a touchdown, and Vavae Malepeai scored the first of two touchdowns on a 2-yard run late in the second quarter that gave USC a lead it would not relinquish.

Chase McGrath, another Mater Dei product, kicked five field goals to tie a school record.

UNLV used early big plays to hang with the defending Pac-12 champions for three quarters. Lexington Thomas gained 71 of his 138 yards rushing on a touchdown run after faking a reverse to freeze defenders and put UNLV ahead 7-6 late in the first quarter.

Armani Rogers threw a 31-yard touchdown pass to Kendal Keys to go up 14-9 after UNLV extended the drive with a 36-yard run by Evan Austrie on a fake punt.

Rogers was 12 of 27 for 97 yards and two touchdown passes, adding 82 yards rushing despite being sacked five times.

''I know - myself, our coaches, our kids - we're now getting on that bus riding home with genuine disappointment in the outcome of the game,'' Sanchez said. ''It does not feel good to play those guys tough for most of the night and walk away with the loss. We feel like we had opportunities to win that football game, and it's been a long time since we've had a team that could actually come out here and do that.''

THE TAKEAWAY

UNLV: The Rebels can run the ball. UNLV finished with 308 yards on the ground, and looked like a team more than capable of making a bowl game for the first time since 2013.

USC: The Trojans need to tighten up on defense, and quickly. Bryce Love, the star running back for No. 13 Stanford, will like his chances to boost his Heisman Trophy candidacy next week against a USC defense that continued last season's penchant for allowing explosive gains.

POLL IMPLICATIONS

USC didn't do much to impress voters in the short term. However, Daniels' improvement over the course of the game bodes well for Helton in his third season, especially with road games against the Cardinal and Texas up next.

PROMPT PORTER

It didn't take long for USC outside linebacker Porter Gustin to make his presence known despite undergoing knee surgery on Aug. 8. He recovered Thomas' fumble on the first play of the game before sacking Rogers on UNLV's third snap. Finishing with 1 1/2 sacks among his three tackles, the senior was a regular presence in the UNLV backfield.

INJURY REPORT

Keys left the game late in the second quarter and was being examined for a possible head injury after landing hard trying to make a diving catch.

Redshirt freshman Brett Neilon started at center for USC, as senior Toa Lobendahn did not dress because of a strained pectoral muscle.

UP NEXT

UNLV: Hosts UTEP on Saturday.

USC: Opens Pac-12 play at Stanford on Saturday. The Trojans beat the Cardinal twice last season, including a 31-28 win in the conference title game.

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