Mets bullpen has been a daily puzzle for manager Carlos Mendoza

DENVER — At this point, it’s a near daily conundrum. The Mets were about to take on the Dodgers this past week and had just exhausted three high-leverage relievers a day earlier. How was the state of Carlos Mendoza’s bullpen?

“That’s a good question,” Mendoza said with a humorless chuckle.

The Mets entered Saturday night’s game against the Rockies still trying to figure it all out, and frankly, it’s been a concern ever since they lost A.J. Minter for the year. It’s not that the bullpen is doing poorly — far from it; the unit’s 2.88 ERA is second in baseball — it’s that they’re plain old tired.

Though their 234 relief innings this season are only 10th in MLB, the Mets are in the midst of playing 10 straight games — and of the eight they’ve completed thus far, six have been decided by two or fewer runs.

It’s not just innings that take their toll but high-leverage innings, and that means Mendoza has had to rely heavily on the circle of trust made up of Reed Garrett, Ryne Stanek and Huascar Brazoban to create the bridge to Edwin Diaz.

“We’ve been using them pretty hard,” Mendoza said. “When you look, especially at a guy like Reed Garrett, I feel like the past week has been on-and- off, on-and-off, and that’s not sustainable. I feel like this is something where we’ve got to be careful here.”

There’s no perfect solution, but there are moving pieces that show the Mets are trying their best to make sure they have the arms they need when it matters most. Paul Blackburn was moved to the bullpen, and he and Brandon Waddell, called up this past week, can eat innings. On Saturday, they acquired two fixer-uppers: righthanded reliever Julian Merryweather, who was signed to a minor-league contract, and righthander Justin Garza, whom they got from the Giants for cash considerations.

Merryweather, who last played for the Cubs, has a career 4.72 ERA in 152 appearances. Garza has a 5.74 ERA in 38 major-league games (he had a 6.11 ERA in Triple-A this year).

“Good arm,” Mendoza said of Garza. “Ability to throw strikes . . . He’s a guy that has options, obviously, but he’s a strike-thrower.”

While neither sounds like a difference-maker, president of baseball operations David Stearns has lived up to his reputation of building strong bullpens out of hidden gems, as evidenced by Garrett (a 0.99 ERA this year despite a 4.33 career mark) and Brazoban, who, at age 35, is having the best season of his career.

“I feel like every other day — I’m not going to complain — but we’re playing so many tie games,” Mendoza said. “Every time that [high-leverage arms] are available, we’re using them. It’s the same thing with Brazoban, so that’s the balance here that we’re going to have to watch those guys closely.”

There is hope, though, that the Mets eventually will get more length from their starters. Sean Manaea (oblique) began his rehab assignment with Class A Brooklyn on Friday, allowing four runs (three earned), four hits and no walks with two strikeouts in 36 pitches in 1  2⁄3 innings. Frankie Montas (lat) will have another rehab outing of 80 to 85 pitches with Triple-A Syracuse on Sunday and at least another after that, Mendoza said.

His last outing, though, was troubling: He allowed five runs in four innings-plus, with four homers on 61 pitches. He struck out three batters and walked one.

“We’ll see how tomorrow goes,” Mendoza said. “Then we’ll start looking at more results and all that. But for now, I think it’s more how they’re bouncing back.”

By Laura Albanese

laura.albanese@newsday.com@AlbaneseLaura

Laura Albanese is a reporter, feature writer and columnist covering local professional sports teams; she began at Newsday in 2007 as an intern.