CARSON, Calif. - Giovani dos Santos is still getting to know his LA Galaxy teammates, and he isn't yet in ideal game shape.

That didn't stop the Mexican playmaker from having a dynamic MLS debut for his loaded new team.

Dos Santos had a goal and an assist Sunday in his first MLS game, leading the Galaxy to a 3-1 victory over the Seattle Sounders.

After setting up captain Robbie Keane's tiebreaking goal in the 47th minute, dos Santos confidently scored his first goal in the 64th minute, taking a beautiful pass from Keane on the run and burying his shot past Stefan Frei.

The sellout crowd at StubHub Center gave a standing ovation when dos Santos left in the 69th minute after delivering the latest big debut for the defending MLS champions.

"We created a lot of chances," dos Santos said. "For me, it's very easy to play with a team like that. ... I think we have a lot of possibility. We can achieve every goal we want. We have a great team."

Dos Santos started up front alongside Keane and took corner kicks as the Galaxy (11-7-7) officially unveiled the newest acquisition in their star-studded lineup. Dos Santos, who also scored a goal in a CONCACAF Champions League match Thursday, even lived up to the standard set by English star Steven Gerrard, who had a goal and an assist in his winning Galaxy debut last month.

With David Beckham watching from a luxury suite, Gyasi Zardes also scored as the Galaxy unleashed the full might of their reloaded roster for the first time. The five-time champs have scored 22 goals in their last five MLS home games, staying in the Western Conference race despite a slow start to the season and continued struggles on the road.

"We have a long way to go," coach Bruce Arena said. "We've played 25 different lineups in 25 games. Hopefully over the next month or so, we start getting in good form. ... Dos Santos is going to take a little time, but I think already the chemistry with his teammates is really good."

Chad Barrett scored in the opening minute for the Sounders (10-12-2), who competed without any designated players after leaving Clint Dempsey and Obafemi Martins at home from the rivalry game. Dempsey strained his hamstring in training Friday, and Martins still isn't quite ready to return from a groin injury.

Barrett also left the game with an injured right hamstring immediately after his stunning opening-minute goal. Zardes equalized in the 13th minute with his 25th career MLS goal.

But the sellout crowd was most eager to see Dos Santos, who wears the No. 10 Galaxy shirt most recently occupied by the retired Landon Donovan. Dos Santos also is likely to play in the midfield at some point, although Arena won't use him there until his match fitness is optimal.

The 26-year-old dos Santos began training with the Galaxy a week ago after arriving from Mexico's Gold Cup title run. The two-time World Cup performer spent the past two seasons with Villareal in La Liga after a career that began in Barcelona's famed La Masia academy.

While dos Santos' European career was inconsistent, the Galaxy have been chasing him for years, believing his combination of offensive flair and Mexican heritage would be an enormous boost on the field and among Southern California's enormous Mexican-American population.

When MLS altered its designated player rules to allow a fourth big-ticket addition this summer, the Galaxy swiftly closed a deal to add even more talent to their side — and dos Santos immediately showed the flair they expect.

Donovan Ricketts made his first home start in three years for the Galaxy, who reacquired the goalkeeper from Orlando City after Jaime Penedo left the club.