SAN FRANCISCO -- Having received just six runs of offensive support in his first five starts for the San Francisco Giants, right-hander Mike Leake had a feeling the club's hitters would have a powerful performance Sunday.

Himself included.

Leake helped his own cause with his sixth career home run, a three-run shot that propelled the Giants to a 10-3 victory over the San Diego Padres and a three-game series sweep.

Catcher Buster Posey drove in two runs with a double and a single as the Giants rang up eight runs or more for the third consecutive game and finished the series with a 27-4 scoring advantage over the Padres.

"I look at myself as one of the nine hitters," said Leake, who entered the game with just a .115 batting average. "I look at myself as an offensive threat. It's no fun hitting .120."

The win allowed the Giants (75-68) to remain 7 1/2 games behind the Los Angeles Dodgers (82-60) in the race for the National League West title with 19 games remaining.

The Padres have lost four in a row and eight of 10.

Leake allowed three runs in the first two innings, including a career-first homer by Padres center fielder Travis Jankowski, before turning things around with his bat in the bottom of the second.

Posey and first baseman Brandon Belt got the inning going with successive singles off Padres right-hander Odrisamer Despaigne (5-9), who was making an emergency start in place of injured right-hander Colin Rea (soreness in right forearm).

Two outs later, shortstop Ehire Adrianza singled in Posey to get the Giants within 3-1 before Leake connected on the first pitch he saw for a three-run homer to left field, giving San Francisco the lead for good.

"Just looking to get a mistake," he said of his offensive approach. "Fortunately, I did."

The home run was Leake's second of the season and gave the Giants' staff a total of eight, the most for any team in a season since the Chicago Cubs had eight in 2006.

The Giants pulled away from there, scoring twice in each the fifth and seventh innings to break the game open en route to the 19th win in their last 24 home games.

Center fielder Angel Pagan scored runs in both innings after stealing a total of three bases. Posey contributed RBIs to each uprising, doubling in third baseman Matt Duffy in the fifth and walking with the bases loaded in the seventh, forcing home Pagan.

Pagan capped his productive day with an RBI single, his second hit of the game, in a two-run eighth. He later came around to score for the third time on Duffy's second hit, an RBI single.

"It's good to see Angel back on track," Giants manager Bruce Bochy said of Pagan, whose three steals were a career high. "He's a different player when he's healthy. He obviously feels good right now. He's playing great ball."

The Giants out-hit the Padres 10-5 in the game and 35-10 for the series.

"The Giants are playing great. They schooled us this weekend," Padres interim manager Pat Murphy said. "I mean, they schooled us in every facet of the game."

Leake (10-8) was tagged for two triples and a double in a two-run Padres first inning and Jankowski's homer to right field with one out in the second before settling down.

He allowed neither another run nor another hit before leaving one batter into the seventh. He walked two and struck out two in his first win as a Giant.

"Good for Mikey," Bochy said. "He's pitched well enough to get a few wins. He took that upon himself. I'm happy for him."

The 10 runs of support helped.

"I'm never really concerned about this team," Leake said of the Giants' offense. "When you look at this lineup, it's pretty good. This offense was really good today."

Third baseman Yangervis Solarte and left fielder Justin Upton had the first-inning triples for the Padres and first baseman Brett Wallace drove in Upton with his two-out double.

Jankowski's homer made it 3-0 and surprised even him.

"Honestly, any home run I hit is kind of a mistake," he said. "I heard it's extremely hard to get a ball out in this park, so when I hit it off the bat, I wasn't thinking it was going out.

"As I was rounding second, I heard the umpire say, 'That's a home run.' I'm thinking, 'Oh, cool. That's a whole different feeling.' But it was the last thing on my mind."

Despaigne, who pitched two innings of relief in the series opener Friday, lasted 3 1/3 innings. He gave up four runs and five hits, walked one and struck out four.

NOTES: RHP Mike Leake became the fourth Giants pitcher to hit a home run this season, joining LHP Madison Bumgarner (five), RHP Tim Hudson (one) and RHP Ryan Vogelsong (one). … The last time the Giants had as many as four pitchers homer in the same season was 1986. ... Padres RHP Odrisamer Despaigne also started a game (April 20) and pitched in relief (April 23) in the same series against the Colorado Rockies earlier this season. ... Before Despaigne accomplished the feat, the last pitcher to pitch in relief and as a starter in the same series twice in the same season was RHP Sun Woo Kim of the Montreal Expos in 2004. ... The Padres have not announced a starting pitcher for Sept. 19 at Colorado. They are hoping injured RHP Colin Rea (soreness in right forearm) will be healthy enough to return to the rotation by then.