LOS ANGELES -- The San Diego Padres' sleeping giant of an offense awoke with a vigorous growl Sunday against the National League West's first-place team.

Left fielder Justin Upton drove in the game's first six runs, and right-hander James Shields took a shutout into the seventh inning, leading the San Diego Padres to an 11-3 rout of the Los Angeles Dodgers at Dodger Stadium.

Upton hit a grand slam and a two-run double to match his career best in RBIs for one game. Center fielder Will Venable collected four hits, and second baseman Cory Spangenberg added three to lead a 20-hit attack that enabled the Padres to break a four-game losing streak.

"We're capable of games like this," San Diego manager Bud Black said. "Early in the year, we showed signs of consistent production, but it's been variable. Yet our guys have shown some resiliency this season."

In the previous eight games, the Padres were shut out three times while getting held to 13 total runs.

"I think we're a very good offense," Upton said. "Sometimes, it's a matter of a little loss of focus and not getting good pitches. But you see what happens when we get good pitches to hit."

Shields (6-0) became just the second pitcher in team history to begin a season with six consecutive wins. Andy Hawkins started 11-0 in 1985.

In the first six innings, Shields allowed just two baserunners -- a hit and a walk -- as San Diego built a 10-0 lead before he allowed Los Angeles to score. Shields finished with seven strikeouts and one walk in seven innings, allowing three runs and five hits.

The Padres began the game by sending eight batters to the plate in the first inning to score four runs on two hits and two walks against right-hander Carlos Frias (3-2).

First baseman Yangervis Solarte led off with a double into the left field corner. Venable and right fielder Matt Kemp followed with walks to load the bases. Upton then propelled a 2-2 fastball over the center field fence for his 12th home run of the season.

San Diego doubled its advantage to 8-0 in the second inning. After singles by Shields, Venable and Kemp loaded the bases with one out, Upton hit a two-run double down the left field line. Catcher Derek Norris then hit a ground ball up the middle through a drawn-in infield for a single that brought home Kemp and Upton.

Third baseman Will Middlebrooks hit his fifth homer, a solo drive into the left field stands in the third, and shortstop Alexi Amarista added a sacrifice fly in the fifth to give the Padres a 10-run lead.

"I just thought we were more patient today," Upton said. "We didn't swing at pitcher's pitches. Obviously, (Frias) a little erratic was erratic early, so we were patient with him and got pitches to hit in the strike zone."

Frias (3-2) tied the team record for most runs allowed by a starting pitcher. In his shortest and worst outing as a starter, Frias conceded 10 runs, 12 hits and two walks, and he did not strike out a batter while throwing 69 pitches in four-plus innings.

"We hadn't seen this at all this year," Dodgers manager Don Mattingly said. "It looked like he had trouble throwing strikes with the fastball. He's gotten hit around before and gotten himself out of it. Today, he just didn't recover."

Despite Frias' ineffectiveness, Mattingly indicated that the right-hander would remain in the rotation.

"We can't make decisions based on one performance," Mattingly said. "That can happen to anybody."

Los Angeles broke the shutout with three runs in the seventh. The Dodgers loaded the bases with no outs on singles from shortstop Jimmy Rollins, second baseman Howie Kendrick and pinch hitter Juan Uribe. Venable, who moved to right field, dived to his right to try to catch Uribe's fly ball, but it glanced off the edge of his glove.

Right fielder Andre Ethier grounded into a double play to