Mets catcher Kevin Plawecki is the first to congratulate Robert...

Mets catcher Kevin Plawecki is the first to congratulate Robert Gsellman on his four-out save as the Mets beat the Braves, 3-0, on Saturday night, Aug. 4, 2018, at Citi Field.   Credit: Kathleen Malone-Van Dyke

What once could have been perceived as a demotion to the bullpen has served as something of a rejuvenating force for Robert Gsellman.

Seth Lugo began 2018 in the starting rotation after Gsellman pitched to a 5.19 ERA in 25 appearances last season, but the castoff quickly made it evident that he could thrive in relief.

Gsellman locked down a four-out save in Saturday’s 3-0 win over the Braves at Citi Field, entering in relief of Bobby Wahl with runners on first and second with two outs in the eighth. He forced Ozzie Albies to ground out to second baseman Jeff McNeil on the first pitch, then got Freddie Freeman, Nick Markakis and Johan Camargo — 3-4-5 in the Braves’ order — all to ground out to McNeil in the ninth.

Initially a middle reliever, Gsellman has climbed the bullpen pecking order, partly due to the trade of Jeurys Familia to Oakland on July 21. Now part of a closer-by-committee based on matchups, Gsellman has excelled.

“Every time I go out there, it’s just same thing, you have to get outs,” Gsellman said after closing out Zack Wheeler’s seven-inning, three-hit gem. “So you put no pressure on yourself and just go out there and have fun.”

Varying degrees of success as a starter — he owns a disappointing 4.60 ERA and unsightly 1.449 WHIP over 156 2/3 innings but also proved useful in his debut in 2016 — have left Gsellman without a spot in the rotation in the near-term. That could always change, but for now, he’s making Mickey Callaway look smart for putting him in the bullpen.

The transition from pitching once every fifth day to being ready at a moment’s notice took time, but Gsellman said he now feels comfortable.

“Just preparing every day, taking care of my body,” Gsellman said. “Some days are tighter than others, and you just have to balance that out, but I’m starting to figure that out and get my groove back.

“I just minimize the throws from practice to the bullpen and save them for the game.”

Callaway showed confidence in Wahl, allowing him to start the eighth inning against Tyler Flowers, the No. 7 hitter. Consecutive singles by Dansby Swanson and pinch hitter Adam Duvall got Wahl in a bind, but the 26-year-old who came over from Oakland in the Familia trade responded by striking out Ronald Acuña Jr., then Gsellman finished the inning.

“I kinda knew when to get loose, so when they called down [to the bullpen], I was just ready to go,” Gsellman said.

A return to the rotation next season seems unlikely, given the way Jacob deGrom, Noah Syndergaard, Steven Matz and Wheeler have all pitched. Corey Oswalt has thrown well in a limited sample, and Jason Vargas is only in the first year of his deal. Of course, injuries could always force the Mets' hand, as they tend to do.

Gsellman has earned his stripes as a reliever. Even if he’d like to return to the rotation at some point, he didn’t make that evident Saturday night.

“I just want to contribute, man,” he said. “I just want to win. We’ve got good arms in this organization, and I’m just ready for the future.”