It was fun while it lasted, which, for Chargers fans fired up to see the team play its first preseason game under a new head coach, in a peculiar new stadium and in a new city, was for about seven minutes Sunday night.

That’s how long it took veteran quarterback Philip Rivers to dissect Seattle’s first-string defense, marching the Chargers 75 yards in 13 plays for a touchdown on the game’s opening drive.

Rivers’ efficiency — he completed five of six passes for 56 yards — and the strong early play of his receivers, tight ends and linemen gave Los Angeles-area fans a glimpse of the kind of explosive offense the Rams could not provide last season.

Then Rivers departed, along with many other starters, and the evening turned sour. The Seahawks reserves badly outplayed those of the Chargers in a 48-17 exhibition victory before a somewhat underwhelming crowd of 21,054 — about 6,000 less than capacity — in StubHub Center.


“I thought we started the game well,” first-year coach Anthony Lynn said. “I definitely didn’t like the way the twos came in. We turned the ball over three times [in the first half]. We stopped playing Charger football.”

There were some bright spots, like backup quarterback Kellen Clemens’ 74-yard touchdown pass to Travis Benjamin in the first quarter, which ended with the Chargers ahead 14-10. Josh Lambo made a 53-yard field goal before halftime, third-string quarterback Cardale Jones had a few nice passes and runs, and rookie cornerback Desmond King had a third-quarter interception.

But the Chargers could not corral versatile Seahawks reserve quarterback Trevone Boykin, who completed 12 of 15 passes for 189 yards and a touchdown and rushed four times for 31 yards and a touchdown.

The Seahawks racked up 458 total yards, compared to the Chargers’ 322. They had 26 first downs; the Chargers had 14. The Chargers lost two fumbles and two interceptions, one that was returned for a touchdown.


Reserve cornerback Michael Davis was beaten deep five times, yielding completions of 27, 18, 28, 34 and 29 yards, and starting middle linebacker Denzel Perryman suffered a first-quarter left ankle injury that left him on crutches and in a walking boot. The severity of the injury was not known.

“I think that’s the reason for preseason, to be able to go back to the drawing board, to see what you can do better,” veteran tight end Antonio Gates said. “Next week, I guarantee you we’re going to put a better foot forward.”

The Chargers’ first steps on their new turf were bold, assertive. Rivers was nearly perfect in his only series, capping his drive with a five-yard third-down scoring strike to Gates, who made a leaping catch in the end zone with cornerback Shaquill Griffin draped over him. Rivers and Gates have combined for 84 regular-season touchdowns, third-most in NFL history.

Rivers got plenty of help on the drive from his revamped offensive line, which provided excellent protection, and running back Melvin Gordon did a nice job of picking up blitzing cornerback DeAndre Elliott on one pass play.


“It was good, balanced football,” Lynn said. “. . . That’s what we’re looking for.”

The rest of the game, not so much.

Clemens’ short pass over the middle bounced off Branden Oliver’s shoulder pads and was intercepted by Terence Garvin, who returned it 37 yards for a touchdown to give Seattle a 10-7 lead late in the first quarter.

After Clemens answered with the scoring bomb to Benjamin, Boykin hit Kenny Lawler with a two-yard touchdown pass for a 17-14 lead early in the second quarter. Tylor Harris intercepted a deflected Clemens pass that led to Blair Walsh’s 28-yard field goal that made it 20-14.


A botched handoff by Clemens in the backfield was recovered by the Seahawks’ Christian French, who returned the fumble six yards to the one-yard line, and Seattle scored on the next play for a 27-14 lead. Boykin scored on a four-yard scramble for a 34-14 lead 49 seconds before halftime.

“You can’t really judge how we’re going to do this year based on what you just saw,” guard Matt Slauson said.

“But it’s obvious we have a lot of work to do.”

Etc.


Reserve defensive end Jerry Attaochu suffered a hamstring injury in the second quarter and did not return. . . . Cornerback Jason Verrett, who is still recovering from knee surgery, and receiver Dontrelle Inman, tight end Jeff Cumberland, running back Kenjon Barner and cornerback Trovon Reed, who are nursing minor injuries, did not suit up.

× The Los Angeles Chargers made their StubHub Center debut with a preseason game against the Seahawks. Reviews from Chargers fans were mixed when asked about the venue.

mike.digiovanna@latimes.com

Twitter: @MikeDiGiovanna