LOS ANGELES — There are better ways to open a Pac-12 Conference season than playing USC at the L.A. Coliseum in the second week of September. It’s a crucial, telling game that arrived far too early on the schedule.

On a brighter note, Stanford has ample time to study the weaknesses revealed in Saturday night’s 42-24 loss to the Trojans. Even with Washington, UCLA, Washington State and Oregon lighting up the scoreboards elsewhere, it’s hard to imagine the Cardinal facing a more well-rounded offense as the season goes on.

The Trojans had racked up 347 yards of offense in the first half, the most Stanford allowed in any half since 2012, and they finished with 623. Too often, it seemed they could run at will against a defensive line that sorely misses Solomon Thomas (now with the 49ers) and is still trying to find its rhythm.

And when the Trojans took to the air, they turned to Sam Darnold, easily one of the top five quarterbacks in the country.

Stanford coach David Shaw was right about Darnold; at times he looks to be in a class by himself. He’s big, agile and creative, with a rocket-like arm and a sense of touch. The Cardinal secondary has been ranked among the best in the country, and some of those defensive backs had their moments Saturday night, but the group was exposed, as well. Darnold completed 21 of his 26 passes for 316 yards and four touchdowns, a showing at times reminiscent of his Rose Bowl masterpiece last season against Penn State.

“We look forward to playing Stanford, it’s a very important game for us,” said Darnold. “They’ve had our number for the last couple of years (three straight wins, each by double-digits). With this big crowd behind us, we really came out fired-up. It was great to see our guys jumping up and down on the sidelines. Super-emotional win.””

The Cardinal knew they could be vulnerable on the defensive line, and their fears were justified as Ronald Jones and Stephen Carr combined for 235 yards on the ground. “Any time you out-rush a David Shaw Stanford team, that’s a special thing, because they know how to run the ball better than anybody,” said coach Clay Helton. “I don’t ever think we can roll up 623 (total) yards, especially against a defense we have so much respect for. We’ve had some hard days in the past against Stanford. I think our guys just had their jaws set to come out and be physical.”

There wasn’t anything particularly alarming about Keller Chryst’s performance. The Stanford quarterback put forth a workmanlike effort and nailed several passes right on target. But the Stanford passing game produced just 172 yards, a fair chunk of it with the game well decided, and was hardly in the same league as the Darnold-driven machine. Quite simply, there was no comparison.

If a single moment stood out for Stanford, it was the sensational, 75-yard touchdown run by Bryce Love to tie the game at 7-7. Behind the textbook blocking of David Bright, Brandon Fanaika and fullback Daniel Marx, Love got his opening and raced down the left sideline to glory.

There will be more of that as the season goes on. Love, who rushed for 160 yards on the night, is very much the “every-down back” forecast by Shaw in the wake of Christian McCaffrey’s departure, combining his breakaway ability with tough running inside. But it’s impossible to rely on the running game when the scoreboard demands a dramatic comeback.

The Trojans, meanwhile, had an impeccable game plan. Studying film during the week, Darnold said, the Cardinal “showed their colors” as far as defensive schemes, resulting in consistent Trojans success on first downs.

“We kind of knew what they were going to bring to the table on first down, and that was a really critical aspect of the game.”

And the band played on. Oh, did the USC band play on, unveiling the same tired riff every 18 seconds or so. It’s not a bit tedious to the Trojans’ fans, however, and on a night like this — recalling so many unstoppable USC performances of the past — even the slightest quibble seemed hollow.

Bruce Jenkins is a San Francisco Chronicle columnist. Email: bjenkins@sfchronicle.com Twitter @Bruce_Jenkins1