OAKLAND, Calif. (AP) -- Oakland first baseman Jason Giambi had gone 50 at-bats without a home run, but he wasn't panicked. Really.

"I wasn't pressing," Giambi said Wednesday after he hit a grand slam and a two-run homer in the Athletics' 10-4 victory over the Padres.

"I knew there was going to be a certain time when I got my opportunity," he said.

Giambi had been stuck at 17 home runs since May 21, when he hit a grand slam against Minnesota. He had just one RBI in his last 13 games and was holding steady at 52.

But in the fourth inning he hit a bases-loaded blast over the right-field fence, then added a two run shot in the seventh to give the A's an interleague sweep of the Padres.

Giambi drove in a career-high seven runs, the most for an A's player since Craig Paquette did it on June 4, 1995, at Baltimore.

"He's had a tremendous year," A's manager Art Howe said. "He's the reason we are where we are. I know of late he's been struggling a bit, but everyone struggles at one time or another."

Scott Service (1-0), recalled from Triple-A Sacramento on May 27, went two scoreless innings for the win. Doug Jones got the last eight outs for his second save.

With the Padres leading 4-3, Matt Clement (5-5) gave up a single to Eric Chavez, who moved to second on Ramon Hernandez's sacrifice. Terrence Long walked and Randy Velarde reached on Phil Nevin's throwing error to load the bases for Giambi.

"I thought the pitch was down, and he went down and got it," Clement said. "It was a great swing, and that's what great hitters do."

It was Giambi's sixth career grand slam and third this season, tying an A's franchise record.

With the A's leading 8-4 in the seventh, Giambi hit a two-run shot off Carlos Almanzar.

Clement lasted just 3 1/3 innings, allowing seven runs on seven hits with five walks and two strikeouts.

The Padres, 1-5 on their six-game American League road trip, took a 3-0 lead in the first inning against Mark Mulder. Tony Gwynn walked with two outs, then scored on Nevin's double before Sprague hit a home run to deep left field.

Matt Stairs' RBI single off Clement at the bottom of the inning narrowed it to 3-1.

Clement walked Jeremy Giambi to start the second, then walked Hernandez two outs later. After Long hit an RBI single to make it 3-2, Velarde walked to load the bases and Clement walked the elder Giambi to tie it. Stairs grounded out to end the threat.

The Padres reclaimed the lead in the third with Gwynn's RBI single.

After Giambi's slam, Hernandez added an RBI single off reliever Brandon Kolb in the fifth inning to make it 8-4.

Mulder went 4 1/3 innings, allowed four runs on five hits, walked three and struck out one.

Notes: The Padres placed right-hander Brian Boehringer on the 15-day disabled list Wednesday with tendinitis in his throwing shoulder. The team recalled right-hander Domingo Guzman from Triple-A Las Vegas to take his place. ... Anthony Gwynn, Tony Gwynn's son, was drafted with the 1,000th pick in the draft by the Atlanta Braves. ... Padres outfielder Eric Owens was out of the lineup for the second straight day with a bruised right thumb. ... Ryan Klesko was out of the lineup for the third straight day because of a bad back. ... A's outfielder Ben Grieve was back in the lineup Wednesday after sitting out Tuesday night's game. It was his first day off after 55 games this season.