Joe Maddon is all for having his young Chicago Cubs team tested in late August. What perfect preparation for the stretch run of September.

Jake Peavy bounced back after falling behind in the first and outpitched Kyle Hendricks, San Francisco's relievers were equally as nasty, and the Giants snapped the Cubs' six-game winning streak with a 4-2 victory Wednesday night.

"You have to understand our young guys are being schooled a bit, and I love it," Maddon said. "It's a good training ground for down the road this year. ... Understand that we have some really inexperienced people that are learning on the fly right now. There's nothing to be worried about or talked negatively about. We're learning and I give our guys credit. We fought again."

Buster Posey followed Brandon Belt's leadoff triple in the sixth with a go-ahead double, helping Peavy win for the second time in six starts.

Peavy (4-6) allowed five hits and two runs, struck out three and walked three in 6 1/3 innings to beat the Cubs for the second time in his last six outings against them. He took a 2-0 loss at Wrigley Field on Aug. 9.

Peavy's bullpen backed him, too, with lefty Javier Lopez contributing his 19th straight scoreless appearance. Lopez and Hunter Strickland each had a strikeout to get through the seventh with runners on second and third, Sergio Romo pitched the eighth and Santiago Casilla finished with a perfect ninth and two strikeouts for his 31st save.

With their first win in six meetings this month against the Cubs, San Francisco avoided its first six-game skid in the series since 1993-94.

"We weren't going to win them all, sorry. I wanted to but I knew it wasn't going to happen," Maddon said.

Kyle Schwarber began the game with a unique, 20-foot double on an infield popup. Peavy and catcher Posey both went for it and Posey got out of the way at the last second, knocking the pitcher over in the process.

Addison Russell popped up in the third and first baseman Belt and third baseman Matt Duffy met on the mound chasing it down, with Belt making the catch.

"We're getting tested, and that's what we came here to do," Russell said.

Hendricks (6-6) saw his winless stretch reach three starts for the Cubs, who lost for only the sixth time in their last 21 road games dating to June 30.

Kelby Tomlinson added an RBI double of his own in the sixth against Hendricks as the Giants ended a three-game slide with their second victory in seven games. Nori Aoki homered for San Francisco.

After Chicago grabbed a two-run lead in the first, Aoki homered to start the bottom half for his fourth career leadoff homer and second this year. He also hit one May 3 against the Angels.

"I don't think it was a secret we needed this one," Peavy said. "When you get those starts every five days they mean the world to you. When you know your team needs you, you do everything you can do. That's not promising anything in the future or even tonight, just the effort level is going to be all it could ever be."