LOS ANGELES » Hawaii’s 2012 football season began not with a whimper but with a bang.

"That was an explosive football team," UH coach Norm Chow said in the aftermath of a 49-10 drubbing from top-ranked Southern California.

A national television audience and a Los Angeles Coliseum crowd of 93,607 watched the Warriors implode in a first-half disaster they could not overcome.

The outcome spoiled Chow’s debut as UH head coach, and doused his return to the Coliseum. Chow was USC’s offensive coordinator for four years, coaching two Heisman Trophy winners and earning a national championship ring.

But the Warriors, who started only one senior, could not keep pace against a USC team led by a Heisman contender.

Quarterback Matt Barkley, who relinquished a chance to enter the 2012 NFL Draft, opened his senior season with this gaudy line: 23-for-38 for 372 yards and four touchdowns. Four of his incompletions were drops. He was not intercepted, not sacked and barely harassed in three quarters of play.

On the first snap of the game, Barkley and receiver Marqise Lee teamed on a simple hitch pattern that ballooned into a 75-yard scoring play.

After that, the Trojans parlayed every Warriors mistake into points, constructing a 35-0 advantage at the intermission.

"We left a lot of points on the table," Barkley said. "It felt like we could have scored 100 points in the first half."

This past spring, Barkley and 14 teammates went on a mission to Haiti, building four houses and working in an orphanage. This fall, Barkley is on a mission to boost the Trojans, who are free to contend for a national title after emerging from a two-year ban on postseason competition.

"We’re playing for our school," Barkley said. "We’re playing for our jerseys."

The Warriors also had hopeful aspirations despite a rebuilding project that included the installation of new offensive and defensive schemes. But it was the basics, not the schemes, that were the pulled strings that unraveled the Warriors.

The Warriors’ first offensive play was the same as USC’s: A hitch pattern into the left flat. UH’s Chris Gant was stopped for a 9-yard gain. USC’s Lee caught Barkley’s pass, sidestepped cornerback Tony Grimes and then, freed when receiver Robert Woods blocked safety Bubba Poueu-Luna, raced along the left sideline for a 7-0 lead.

"It’s a nice, easy throw, and he just made a heck of a move," Chow said of Lee. "He’s a tremendous player."

Grimes said: "I just missed the tackle. Simple as that. No excuses. It was an open-field tackle I should have made, and I didn’t make it. Against a team like that, you can’t make a mistake. You make a little mistake, they’re going to capitalize on it."

Indeed, the Warriors inadvertently contributed to much of the Trojans’ success. Grimes was called for pass interference twice on an extended drive that culminated in Woods’ 20-yard scoring catch.

Later, Gant could not grasp a pass on the left side. A play later, a pass in his direction on the right side was tipped from him. Hayes Pullard, who moved to middle linebacker two weeks ago, grabbed the football and sprinted 27 yards to the end zone on the interception return.

The Warriors then drove to the USC 27. But the handoff between quarterback Sean Schroeder and running back Joey Iosefa was mishandled. The Trojans recovered the fumble and, five plays later, running back Silas Redd scored on a 31-yard run. That was one of two USC touchdowns on fourth-down plays.

"They had nice calls," Chow said, "but we have to stop that."

The Trojans also benefited from two calls.

On fourth and 1, Iosefa, who was aligned as an upback in an apparent punt attempt, moved up, took the snap and barreled for 3 yards. But the officials ruled it was an illegal procedure, although they were vague in the description. The Warriors then were forced to punt.

"They said it was something about an illegal number," Iosefa said.

Chris Demarest, who coordinates UH’s special teams, said: "I need clarification. We broke the huddle. The officials in preseason told me as long as we break the huddle, I’m fine. We all got set. It wasn’t like anybody wasn’t set. It was a quarterback sneak. That’s all we did. It wasn’t an illegal formation."

The Warriors finally scored their first touchdown on an 18-yard pass from Schroeder to Scott Harding at the end of a 12-play drive in the third quarter.

But on the ensuing kickoff, Lee caught the ball 3 yards deep in the end zone, found a lane on the right side and raced for a touchdown. Until that point, the Warriors had been out-playing the Trojans on special teams, particularly with Harding — playing in place of suspended Alex Dunnachie — delivering rugby-styled punts.

"We did well except for letting that dag-gone kick return get away from us," Demarest said. "That’s going to haunt me."

The Warriors managed to play better in the second half, overcoming what Chow had described as "jitters."

In the first half, the Warriors struggled to find the right defensive coverage. When they were in a two-deep zone, the Trojans would search for open seams. They also had to limit their blitzes because of Barkley’s quick release and elusiveness.

"Some of the mistakes we made were magnified because they have such great players," defensive coordinator Thom Kaumeyer said.

Lee finished with 10 catches for 197 yards. Woods caught two touchdown passes.

"Those guys were making plays all spring and all summer," Barkley said. "You expect them to make big plays tonight."