NEW YORK -- “They’re relentless.”

That’s how manager Mickey Callaway described his offense after the Mets posted an emphatic 9-2 win over the Indians -- another team in the thick of the postseason picture, albeit in a different league -- on Tuesday night at Citi Field.

What began as a tight affair between New York’s Steven Matz and Cleveland’s Shane Bieber -- who went toe to toe with nearly identical stat lines through five innings -- turned on its head starting in the sixth, when Michael Conforto hit a tiebreaking two-run homer after Indians left fielder Oscar Mercado dropped a routine fly ball earlier in the frame.

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But instead of resting on their laurels and letting their bullpen close out a close win, the Mets made sure to put the game out of reach with a four-run seventh inning against Cleveland’s bullpen. All but one hitter -- J.D. Davis -- came to the plate in the frame, as Amed Rosario, Joe Panik and Pete Alonso provided the damage from the top of the order with run-scoring hits.

Davis had already done his part, launching a towering 447-foot, two-run homer to center -- tied for the second-longest long ball of his career -- to give the Mets an early lead in the second inning.

“They’re relentless in their approach no matter who comes in, and they’re up there grinding it out,” Callaway said. “Timely hitting, and then you get to their lesser pitchers and you add on. That’s what good teams do -- they add on. And tonight we added on enough to the point where we could stay away from [Seth] Lugo and [Edwin] Diaz, and now we’re set up in a better situation tomorrow because our hitters are relentless.

“We could pop the two-run homer and then sit back and say, ‘OK bullpen, here you go.’ They don’t do that. They score late, they score often, and that takes the pressure off.”

Even though they were up against Bieber, the latest ace of Cleveland’s rotation, the Mets were unfazed. Seven of the nine starters contributed at least one hit on the night, excluding Juan Lagares, who walked twice, and Matz, who allowed just two runs (one earned) while striking out seven in 6 1/3 innings pitched. By snapping Bieber’s four-start road winning streak, New York continued its own string of success at home, winning for the 11th time in its past 12 games at Citi Field to move to 35-21 at home this season.

As the Mets have surged back into contention since the All-Star break, it has been their offense that has led the way. Entering Tuesday, New York led the Majors with a .301 batting average, ranked third in OBP (.362) and was tied for fifth in RBIs (96) and runs (99) in August. With the victory, the Mets improved to 25-10 since the Midsummer Classic.

“We’ve had a feeling, over this run that we’ve been on, that we might not get them the first time through the order, but our lineup has been so good,” Conforto said. “Our hitters have been able to figure out ways to get on base, figure out ways to get runs in. We just have that feeling that eventually we’re going to get through whoever’s on the mound. Regardless of who’s pitching, we feel like we’re going to put a lot of runs on the board.”

It was exactly the type of opening performance the Mets were looking for to begin this crucial nine-game homestand, which also includes series against the National League East-leading Braves and the Cubs, who are two games ahead of the Mets for the NL’s second Wild Card spot.

“I think we all knew that, even it’s August, but playoffs started today,” Davis said. “We have to have that playoff mentality, that playoff atmosphere, that every game counts, especially [with] the hole that we dug ourselves into. I think the elephant in the room is, we got a lot of home games, but a lot of games against playoff teams. And again, back to it, this is our playoff time. We have to play well and we have to come out ready to play.”