The Phillies, 13-2 against NL West teams, protected their wild-card lead, which was a half-game over San Francisco entering the day. San Diego, which has lost three straight games for only the second time this season, led the Giants by six.
Brad Lidge pitched a perfect ninth for his 18th save in 23 chances. On Friday night, Lidge balked in the tying run with two outs in the ninth to blow the save, but the Phillies won 3-2 in 12 innings.
Victorino, who was with the Padres in 2003, hit an RBI single in the fifth. Jayson Werth scored on both of Victorino's hits. Victorino, the center fielder, also threw out Nick Hundley at the plate to end the Padres' fifth.
It was Philadelphia's 10th win in its last 11 games at Petco Park. The Phillies are 17-4 at the downtown ballpark since it opened in 2004.
Joe Blanton (6-6) held the Padres to one run and six hits in six innings, with three strikeouts and one walk. He got only his fourth decision (3-1) in his last 12 starts. Blanton and three relievers retired the final 11 Padres batters.
Garland (13-9) didn't allow a hit until the fifth, when Victorino singled to center with one out to bring in Werth. Werth was hit on the wrist by a pitch leading off the inning and walked slowly to first. He advanced on Raul Ibanez's groundout.
With the score tied at 1, Werth walked leading off the seventh and scored when Victorino's one-out drive bounced past diving center fielder Chris Denorfia and rolled to the fence for a triple, chasing Garland. Left-hander Joe Thatcher intentionally walked pinch-hitter Carlos Ruiz and made way for Luke Gregerson.
Victorino scored when the Padres couldn't turn a double play on pinch-hitter Mike Sweeney's grounder to shortstop. The Padres forced Ruiz, but his slide took out second baseman David Eckstein, whose throw to first wasn't in time to get Sweeney.
Garland, who had won his previous three starts, allowed three runs and three hits in 6 1-3 innings, with three walks and two strikeouts.
Garland singled in Denorfia with two outs in the fifth to tie the game at 1. Hundley tried to score from second on Eckstein's single to center, but Victorino's one-hop throw nailed him at the plate to end the inning.
NOTES: Garland is 0-5 with a 7.27 ERA in six career starts against the Phillies. ... Padres RHP Mat Latos, who held the Phillies to one run Friday, has allowed three or more runs only once in his last 20 games, when he gave up three to the Phillies on June 4. According to the Elias Sports Bureau, only two other pitchers in major league history have allowed no more than two runs 19 times in 20 starts, and neither of them did it within one season: Greg Maddux (1993-94) and Roger Clemens (1990-91). ... Giants ace Tim Lincecum has lost five straight starts, which has helped the Padres. According to Elias, the last Giants pitcher to go at least 0-5 with an ERA of 7.80 or higher for a month was Bud Black, now in his fourth season as Padres manager. Black was 0-6 with an 8.01 ERA in September 1992.