Lucas Sims won at mile-high altitude last week and won Tuesday on the other side of the northern Atlanta suburbs from his hometown of Lawrenceville.

The former Brookwood High School star pitched six innings of three-hit ball and Nick Markakis homered and drove in two runs to lead the Braves in a 4-0 interleague win against the Mariners at SunTrust Park.

“It’s pretty special to win in my backyard, per se,” said Sims (2-3), who had two walks and four strikeouts and worked out of trouble in four consecutive innings for his first home win in the 23-year-old prospect’s fifth major league start.

The Braves scored a run in each of the fourth through seventh innings on their way to evening the three-game series. The Mariners’ sloppy defense hardly looked like that of a team that came in just one game behind the American League wild-card leaders.

Sims, a first-round draft pick in 2012 who made his major league debut on Aug. 1, recorded his first major league win Thursday at Colorado when he limited the Rockies to two runs while allowing five hits and three walks in five innings. He worked out of jams in three of his five innings at Colorado and did similarly impressive maneuvering Tuesday.

“The kid never stops pitching,” Braves manager Brian Snitker said. “I mean, he doesn’t get flustered. He pulls that hat down and goes to work. He competes and gets after it and just keeps trying to make pitches.”

Opposing hitters are 0-for-11 with runners in scoring position and two outs in his first five starts.

“He’s had that since Day 1 that he’s been up here,” catcher Tyler Flowers said of Sims’ composure. “That’s something that’s giving him a chance to bounce back from tough outings, to move on to the next pitch – that’s hard to do. Some veterans don’t do that. I think that’s something big just to allow him to be consistent over the course of his career.”

After going 0-3 with a 5.71 ERA and getting a total of four offensive support runs in his first three starts, Sims is 2-0 with a 1.64 ERA in his past two starts and the Braves scored seven runs while he was in those games.

For a while Tuesday it looked like the Braves were inclined to fritter away scoring chances of their own, something they did all too frequently while losing 23 of their previous 33 games. After Freddie Freeman extended his hitting streak to 11 games with a two-out single in the first inning, Matt Kemp followed with a single before Markakis struck out against left-hander Marco Gonzalez.

A baserunning blunder in the second cost the Braves a potential run. After Ender Inciarte was caught stealing with Freeman batting in the ninth inning of a one-run loss Monday, Tyler Flowers was caught trying to steal third base for the second out of the second inning Tuesday with Dansby Swanson batting — not the Braves’ last mistake on the bases.

“I don’t know, he thought he was invisible or something,” Snitker said, maintaining his humor. “I don’t think he thought they were paying attention to him. And I think he might have broke down a little bit or he’d have been safe. I mean, it was a perfect pitch (fastball) for the guy to throw on. But still.”

Swanson immediately followed with a single up the middle with no one on base and Sims on deck (Sims struck out).

Monday night, Snitker said the Braves’ aggressive baserunning wasn’t necessarily a bad thing. But….

“They can take that to an extreme, too,” he said Tuesday. “We can’t continue to do that, we’re lucky we got away with it tonight. It’s just something we’ve got to be a little more aware of. It’s something we haven’t done all year; we’ve been pretty good about running the bases very well and intelligently, and the last couple of days we haven’t done that.”

The Braves also failed to score after getting a runner to second with less than two out in the third inning, after Brandon Phillips hit a one-out single and stole second with a creative, athletic slide to avoid the tag. Freeman struck out and Kemp grounded out to end the inning.

But Markakis took matters into his own hand in the fourth when he hit a leadoff homer on a full-count pitch from Gonzalez, making it three consecutive homers for Markakis off lefties after he’d hit just one against a lefty in his first two seasons with the Braves. Five of Markakis’ eight homers this season have given the Braves a lead.

One inning later, Markakis came through with an RBI single with runners on the corners and two out. His hit scored Freeman, who had walked with two out, but then Kemp was thrown out trying to go from first to third on the play.

Markakis has hit .333 (30-for-90) with eight doubles, three homers, 16 RBIs and a .940 OPS in his past 25 games.

The Braves added a run in the sixth when Ozzie Albies was caught in a rundown between third and home but Mariners third baseman Kyle Seager dropped a throw as Albies approached him at third base. The speedy rookie turned and dashed home when the ball rolled away from Seager.

Freeman’s RBI single in the seventh drove in another unearned run after Phillips hustled to second base for a two-base error on center fielder Mitch Haniger on a dropped fly ball.

Sims, meanwhile, looked unusually comfortable and composed in tight spots again. The Mariners had at least one runner on base with less than two outs in the second, third, fourth and fifth innings, and each time Sims worked around the traffic and came out unscathed. He gave up a one-out single in the second inning, a leadoff walk in the third, a leadoff double in the fourth and a one-out single and two-out walk in the fifth.

The Mariners got zilch out of all those chances. Sims retired each of the next three batters after the leadoff hitter reached in the third and fourth innings and induced an inning-ending groud-out from Yonder Alonso to end the fifth.

“I think if you just stay in control of your emotions,” Sims said, “and focus on the task at hand, one pitch at a time – it’s cliché, but executing one pitch at a time, trying to get soft contact, I think that helps get you out of a lot of jams.”

Seatts was 0-for-7 with runners in scoring position after going 21-for-55 while winning five of its previous six games.