CHICAGO — Coming back from an oblique strain in less than three weeks is a tall order for any hitter, as Brian McCann learned in his first 10 games back with the Braves.

He vented some frustration against the Chicago Cubs on Thursday, driving in four runs with a pair of homers in an 8-3 win that gave the Braves another series victory at Wrigley Field.

“He came in after the first homer and said, ‘I think I’ve got my stroke back,’” said manager Fredi Gonzalez, whose Braves won three of four games in the series and have won 14 of their past 18 to build a commanding lead in the wild-card race.

Michael Bourn matched a career high with his first four-hit game since being traded to the Braves, who trimmed a half-game from idle Philadelphia’s lead in the National League East.

The Phillies are six games ahead of the Braves, who lead San Francisco by nine games in the wild-card race, pending the outcome of the Giants’ late game against Houston.

McCann snapped an 0-for-15 skid with a three-run homer in the first inning off Matt Garza (6-10) and added a solo homer in the seventh off left-hander John Grabow, his third multi-homer game this season.

“I just haven’t really swung the bat that great since coming off the DL,” said McCann, who had a .139 average with two homers and three RBIs in 10 games since returning to the lineup. “When you don’t feel good and you face good pitching, that’s going to expose you. I’ve been working in the cage the last three or four days trying to find it, and today I made strides.”

McCann and the Braves provided more than enough support for Braves rookie Brandon Beachy (7-2), who gave up three runs (two earned) and six hits in six innings. He went to 4-0 with a 2.55 ERA in his past seven starts, and praised his All-Star catcher.

“What more can you ask for out of anybody?” Beachy said. “He puts us on his back and carries us some days. And then he’s tremendous behind the plate, all at the same time. It’s nice to have.”

After Bourn singled to start the game and Martin Prado reached on an error, McCann hit a homer into the teeth of a stiff wind blowing in from right field. It sounded like a shotgun blast coming off the bat, and put the Braves ahead 3-0 before the first out.

The Cubs quickly erased the lead with an unearned run in the first inning and two runs in the second, when Marlon Byrd homered and Tyler Colvin tripled and scored on a groundout.

Beachy settled down after that and faced only two batters over the minimum in his final four innings, finishing with eight strikeouts and no walks.

McCann has 22 homers after hitting 21 in each of the past two seasons and 23 in 2008. He had a career-high 26 homers in his first full season in 2006.

Before straining his oblique July 26, he had hit .319 with 12 homers and 25 RBIs in his past 38 games. Two weeks later he began a three-game rehab assignment, then was back with the Braves.

The majority of oblique strains require a month or more of recovery time.

Until Thursday, he didn’t have more than one hit in any game since returning and had seven strikeouts and three hits in 25 at-bats over his past seven games.

“I went down to the [batting] cage this morning,” McCann said. “It was the first time [since the DL] that I was able to go up to the plate and know I’m going to put together a good at-bat. The first three games here I was just scuffling.

“Something clicked in the cage today, and I was able to bring it to the game.”

Despite the recent slump, McCann has a .292 average and leads the Braves with an .877 on-base-plus-slugging percentage.

“Hey, everybody goes through that stuff,” Gonzalez said. “Guys that win MVPs and batting titles, over the course of the year they’re going to have an 0-for-15 someplace, or a 1-for-22. I’m glad he’s back swinging. Two home runs, one of them opposite field, which is nice to see.”