Robert Gsellman of the Mets pitches against the Braves at...

Robert Gsellman of the Mets pitches against the Braves at SunTrust Park on Sept. 17, 2017, in Atlanta. Credit: Getty Images / John Amis

ATLANTA — Robert Gsellman’s season has been an exercise in inconsistency, one that has confounded the Mets, who just a year ago believed they had unearthed a potential rotation mainstay.

But Gsellman took a small step toward restoring that faith Sunday, handcuffing the Braves over seven strong innings in a 5-1 win that gave the Mets their first series victory on the road since mid-August.

“He’s being challenged by something right now, and that is he hasn’t had the kind of year that he anticipated or we anticipated,” manager Terry Collins said. “Right now, he’s got to show us that he can be one of those guys again. And today, he showed us he could.”

Gsellman, 24, surrendered only an unearned run in the seventh when rookie shortstop Amed Rosario misplayed consecutive grounders. Otherwise, he looked like the pitcher who emerged in the second half last season, allowing three hits, striking out three and walking none.

“I thought I worked well out of it, tried to pick up Rosario after a couple of errors,” Gsellman said. “We all make mistakes. You have to pick up your teammates sometimes.”

The performance came after he walked a season-high five batters in a loss to the Cubs.

By taking two of three against the Braves, the Mets (64-85) captured a road series for the first time since they won two of three Aug. 10-13 at Philadelphia.

The Mets opened a 2-0 lead against Julio Teheran in the first when Jose Reyes lined an RBI triple and scored on Rosario’s groundout. Teheran lost for only the second time in his last six decisions against the Mets.

The Mets tacked on three runs in the ninth. September call-up Phil Evans got his first major-league RBI with a double and Asdrubal Cabrera followed with a pinch-hit homer to push his hitting streak to 11 games.

After getting bombed for a franchise-worst 39 runs in a three-game sweep by the Cubs to begin this road trip, the Mets surrendered only seven runs in three games against the Braves.

Gsellman (7-7, 5.22 ERA) equaled his season high with his seven-inning stint, his longest outing since May 29. He effectively threw his two-seam fastball inside, which at times has been a challenge.

“He moved the ball around today so well . . . He got some guys rolling over and conserved pitches,” Collins said. “Didn’t get behind in a lot of counts. I thought he was outstanding.”

Gsellman paired his grounder-inducing two-seamer with an improved changeup, the result of a grip change he made in the minors earlier this season while rehabbing from a hamstring injury.

Gsellman hopes for a strong finish to a season marred by inconsistency and comments that indicated that he didn’t care about his lackluster results during a rehab assignment. General manager Sandy Alderson did not hide his displeasure, and the pitcher apologized.

Said Gsellman: “Just trying to finish strong with these guys so we can get good momentum for next spring and just keep it rolling.”