At Turner Field on Monday, it would’ve been difficult to find anyone who labored as much or as ineffectively as Mets pitcher Daisuke Matsuzaka.

Braves hitters vented recent frustrations by pounding the fading former Red Sox standout for seven hits and six runs in the first three innings of a 13-5 series-opening rout against New York, matching their highest run total of the season.

Freddie Freeman’s three-run homer in the second inning pushed the lead to 6-1 for the Braves, who bounced back from Sunday’s 7-0 loss to the Marlins with an outburst that matched their highest runs total this season.

The win and the Nationals’ loss to the Phillies dropped the Braves’ National League East magic number to 11.

“You never want to get shut out, but when we do, when you come out here and score six in the first two innings, that kind of takes a little weight off your shoulders, and you can just go out there and play the rest of the game,” said Freeman, who also had a two-run double in the first inning and matched his career-high with five RBIs.

Freeman ranks fourth in the league with 93 RBIs, only one away from the career high he set last season.

“He gave us a couple of great at-bats,” Braves manager Fredi Gonzalez said. “On a tough day to play, really. The first two innings almost took an hour. Both (pitchers) weren’t around the plate. He gave us great at-bats and put us on the board.”

Any combination of Braves wins and Nationals losses totaling 11 would give the Braves their first division title since 2005, and they hope to have their offense humming again as they near the postseason.

It was tough to gauge much Monday against an injury-depleted Mets team that arrived at their Atlanta hotel at 4 a.m., after playing a night game at Washington, and against a pitcher (Matsuzaka) with a 10.95 ERA in three starts since signing with the Mets. But the Braves were nonetheless encouraged by a couple of developments on a day when they matched their season-high scoring total.

Leadoff hitter Jordan Schafer had four hits and equaled a career high with three stolen bases before leaving with a low-back strain after a seventh-inning single. He was listed as day-to-day, but Schafer said his back just spasmed and that he expected to be back in the lineup Tuesday.

Schafer stole three bases in the first four innings to raise his team-high total to 20, or 38 percent of the Braves’ total.

“I’m not on the bases for decoration,” Schafer said, smiling. “When I get on there I’m trying to go. As fast as I can. I’m not trying to wait around and stand there, I’m trying to take off.”

Long-slumping B.J. Upton continued his recent encouraging signs with a pair of doubles for the Braves, who’ve won 19 of 23 home games and improved their majors-leading records to 84-53 overall and 50-19 at Turner Field.

“He’s been swinging the bat great,” Freeman said of Upton, the center fielder who’s 9-for-21 with a homer and four RBIs in his past six games, including an RBI double Monday. “You could tell in (batting practice) last week that he was almost there. He was back-spinning balls to right-center. He was just on the verge of breaking out, and now here he goes.

“He seems to do well in September, and he’s getting hot again. That’s just what we need, so hopefully he can carry that on.”

Braves starter Paul Maholm (10-10) won for the first time in two months, though he needed 100 pitches to get through five innings. With both pitchers working slowly and throwing a lot of balls, the first 3 1/2 innings took one hour and 45 minutes. The game lasted 3:41.

Maholm, who was 0-4 with a 7.30 ERA in his previous five starts, allowed six hits, three runs and three walks with four strikeouts to continue his success against the Mets. He’s 7-4 in 14 starts against them, 4-1 with a 1.31 ERA in the past six.

“Sometimes you go out there and you’re not in rhythm, and you’ve just got to battle,” Maholm said. “Today was one of those days. Luckily the offense put up so many runs that my five-and-dive wasn’t a big deal.”