LOS ANGELES, Calif. - Justin Upton erupted Sunday, in a positive way for the San Diego Padres.

Upton hit a grand slam and drove in six runs as the Padres broke loose, backing unbeaten James Shields in an 11-3 win over the Los Angeles Dodgers.

A day after being ejected for arguing balls and strikes, Upton tied his career high for RBIs. He hit a slam in the first inning before Carlos Frias recorded an out, then added a two-run double in the second.

The Padres had totalled just three runs in losing four straight games. Upton was tossed Saturday night as San Diego was shut out on one hit.

"I don't think we cared how we got our runs today. But it was nice to get some runners in scoring position, get the bases loaded and get some hits in those situations," Upton said.

Will Middlebrooks homered to help stake Shields (6-0) to a 9-0 cushion through three.

"I'll take that every start," Shields said. "When you get an early lead like that, you've still got to bear down and keep making your pitches. That team over there is too dangerous to take lightly.

The All-Star right-hander became the first Padres starter to win his first six decisions since 1985, when Andy Hawkins began 11-0.

New to the Padres this year, hasn't lost in 10 starts. He has given up a major league-most 15 home runs — Alex Guerrero connected in this game — and has a 3.75 ERA.

Shields also went 6-0 over his first 13 starts in 2007 season with Tampa Bay.

Shields allowed three runs in seven innings and struck out seven. He started a four-run burst in the second inning with a leadoff single.

Frias (3-2) was tagged for 10 runs and 12 hits in four-plus innings.

The 25-year-old rookie right-hander put himself in the Dodgers' record book alongside Brad Penny, Tom Candiotti, Chan Ho Park, Carlos Perez and Odalis Perez as the only starting pitchers to give up as many as 10 runs in a start since the franchise moved to Los Angeles in 1958. Penny was the last one to do it, on May 7, 2008, against the New York Mets.

"Carlos has gotten himself out of a couple of those this year where he recovered. This time he didn't recover," Dodgers manager Don Mattingly said. "But this could happen to anybody. You get yourself in bad counts, sometimes you pay for it. Sometimes you don't, and they pop it up."

Frias found himself in a bases-loaded jam after 13 pitches, giving up a leadoff double by Yangervis Solarte and two walks. Upton drove a 2-2 pitch to centre field for his 12th homer this season and fourth career slam.

"Justin's been phenomenal. He's been taking the boys and putting them on his back," Shields said. "He's an All-Star calibre player and he's doing his job. But we need some other guys to step up as well. We've just been in a rut right now."

It was the first slam against the Dodgers since Sept. 14, 2013, when Hunter Pence victimized Stephen Fife en route to a 19-3 Giants victory — the most runs ever scored by an opponent at Dodger Stadium.

The Padres, coming off their sixth shutout loss in a span of 18 games, extended their lead to 8-0 in the second. Upton hit a bases-loaded two-run double inside third base, and Derek Norris followed with a two-run single through a drawn-in infield.

Jimmy Rollins' one-out single in the first was the Dodgers' only hit until they scored three times in the seventh. Guerrero hit his seventh homer.

TRAINER'S ROOM

Padres: RHP Brandon Morrow, who hasn't pitched since May 2 because of inflammation in shoulder, threw 45 pitched during a bullpen session and is scheduled to pitch a simulated game sometime this week. ... 1B Yonder Alonso, is scheduled to begin a minor league rehab assignment this week after missing 15 games with a bruised right shoulder. ... OF Wil Myers remains on the disabled list with tendinitis in his left wrist.

Dodgers: Catcher Austin Barnes made his major league debut, one day after Yasmani Grandal went on the seven-day concussion disabled list. Grandal, injured in Friday night's series-opening 2-1 victory, is expected to be activated after a minor league rehab stint that will last two or three games.

UP NEXT

Padres: RHP Tyson Ross (2-4) opposes Jered Weaver on Monday night in the opener of a three-game interleague series with the Angels that concludes the six-game road trip.

Dodgers: LHP Brett Anderson (2-2) takes the mound against RHP Williams Perez on Monday night in the opener of a three-game set with Atlanta Braves.