Buster Posey hit a tiebreaking RBI single on the night he received a prestigious award and the San Francisco Giants reduced their magic number for clinching the NL West to two with a 5-1 victory over the San Diego Padres on Friday.

Posey was honored in a pregame ceremony with the "Willie Mac" award as the most inspirational player on the team. He then delivered another big hit when he drove in Marco Scutaro with a single off Casey Kelly (2-2) that gave San Francisco a 2-1 lead in the fifth inning.

That helped Ryan Vogelsong (13-9) match his career high in wins and put the Giants in position to clinch a division title as early as Saturday. San Francisco would win the West on Saturday night with a win if the Los Angeles Dodgers lose earlier in the day to Cincinnati.

Pablo Sandoval belted his fourth home run in three days, and Brandon Crawford and Scutaro had RBI singles as San Francisco matched a season high with its fifth straight win.

Chase Headley hit a solo shot for his 29th homer for the Padres. But he was thrown out at home trying to score the tying run on Yasmani Grandal's two-out double in the sixth. The Giants cut him down with a well-executed relay from left fielder Gregor Blanco to Crawford to Posey, who fielded the throw on a short hop and tagged Headley to preserve a 2-1 lead.

Vogelsong, who had a 10.31 ERA over his past seven starts, reversed his recent slide by allowing just one run and five hits in six innings.

The Giants broke it open with three runs in the sixth, capped by Sandoval's homer. After going 161 at-bats without a long ball, Sandoval has regained his power stroke this week and now has 12 homers this season.

It was a big day all around for Posey, who won the award named after Hall of Famer Willie McCovey that is voted upon annually by Giants players, coaches, training staff and the fans.

Posey also got a boost in his bid to win the batting title when teammate Melky Cabrera requested to be disqualified from the NL honor. Major League Baseball and the players' association agreed to a one-season-only change in the rule governing the individual batting, slugging and on-base percentage champions.

Serving a 50-game suspension after testing positive for testosterone, Cabrera leads the league with a .346 average. Cabrera had 501 plate appearances, one short of the required minimum if the Giants play 162 games, but would have won the title under section 10.22(a) of the Official Baseball Rules if an extra hitless at-bat were added to his average and he still finished ahead. With Friday's agreement, that provision won't apply this year to a player who "served a drug suspension for violating the Joint Drug Program."

Posey, who is hitting .335, trails Pittsburgh's Andrew McCutchen by three points for the NL lead with less than two weeks left in the regular season.