SAN FRANCISCO -- Oh, Buster Posey knew all about how long he had gone without a home run.

"Yeah, I've had a few reminders over the last week or two," Posey said with a chuckle.

All that talk about the star catcher's second-half power drought was answered with one mighty swing in a September game that mattered, and his two-run shot helped the San Francisco Giants beat the St. Louis Cardinals 8-2 Friday night in a matchup of playoff contenders.

Posey drove in four runs and the Giants stayed four games back of the NL West-leading Los Angeles Dodgers, who won at Arizona. San Francisco maintained its one-game lead over the New York Mets for the league's top wild card, moving three games up on the Cardinals in the wild-card standings.

Left-hander Matt Moore (4-4) allowed two runs over five innings, struck out four and walked three while facing the Cardinals for the first time in his career. He won for the fourth time over five starts in his ninth outing since joining San Francisco in a trade with Tampa Bay.

Posey was all smiles in the dugout after his fourth-inning drive, his first home run in 185 at-bats and exactly two months -- he last connected on July 16 at San Diego.

"It was a good feeling," he said.

Posey also had a two-run single and followed up his four-hit game Thursday night with three more.

"It was great to just see him start smiling and laughing after he touched home plate," Brandon Belt said. "It's kind of out of the ordinary with him. He's pretty stone-faced most of the time. When you know what he's capable of doing and when he's had a stretch like he's had, it's good to see."

Belt hit a two-run double to highlight San Francisco's six-run third. Posey singled in a pair of runs that inning, when all the runs were unearned off rookie right-hander Luke Weaver (1-3).

For the second straight day, Giants manager Bruce Bochy gave his team a late report time to the ballpark and the players went without batting practice. This time, it came on the heels of Thursday's 6-2 victory behind Johnny Cueto's five-hitter.

"A couple days off the field will serve them well," said Bochy, who is sticking with the same routine for Saturday night's game.

It proved the right call again. After a demoralizing three-game sweep by San Diego earlier this week, San Francisco suddenly looks like a playoff team again. The Giants have had World Series-winning seasons in every even year this decade: 2010, `12 and `14.

Weaver's night was done after 2 2/3 innings and he is winless in four starts since beating Oakland on Aug. 26. He allowed five hits, struck out four and walked two.

Yadier Molina drove in both runs for the Cardinals, including a bases-loaded walk in the fifth.

"We just have to play better, that's all there is to it," manager Mike Matheny said. "The standings are the standings and we know what they are. You can't run from them, hide from them. The standings say we're right there, so just keep playing the game. That's all it is. Same as always."

Denard Span hit eighth for the Giants again after his strong performance, with a two-run single among his two hits in that spot a night earlier.

NINTH-INNING DELAY

A fan ran on the field in the top of the ninth and a member of security who slid approaching the man had to be helped off the field with an injury.

TRAINER'S ROOM

Cardinals: OF Matt Holliday will face live pitching Saturday with the hope he still might return from a broken right thumb as St. Louis makes a playoff push. The slugger hasn't played since Aug. 11, when he was hit by a pitch in an 11-inning loss to the Cubs. He had surgery to insert a screw for the fracture. "I'd love to play but I can't do it at jeopardizing putting my finger in a bad situation," Holliday said. "It's clearly not 100 percent. It's still fractured but there's a screw in there. It's more stable than it would be if I had not had the surgery." ... SS Aledmys Diaz returned to the lineup after being held out Thursday. He came off the disabled list Sunday after he had been sidelined since July 31 with a broken right thumb, and the medical staff and Matheny are being cautious to determine if Diaz can handle playing every day.

Giants: The team activated OF Gregor Blanco from the 15-day disabled list after he missed 22 games with a right shoulder impingement. ... Bochy has been looking to rest Posey and will aim to give him a break in Sunday afternoon's series finale following a night game Saturday.

UP NEXT

Cardinals: RHP Mike Leake (9-10, 4.60 ERA), who spent the second half of last season with San Francisco, looks for his second win in seven starts since July 29.

Giants: RHP Jeff Samardzija (11-10, 4.07) seeks his first victory in four starts since Aug. 26. He is 4-4 with a 4.61 ERA in 20 career outings vs. St. Louis, losing to the Cardinals on June 4.