NEW YORK — When you trade away half your bullpen in the middle of the summer — and then lose your closer to injury — it’s natural to expect your relief corps to perform worse.Instead, a New York Mets bullpen without its go-to arms from the first half of the season has actually been better over the last month. New York’s bullpen had been its strength through a disappointing first four months, posting a 3.81 ERA. Without Luke Weaver, A.J. Minter, Brooks Raley and Huascar Brazobán, and with Devin Williams on the injured list much of the time, that pen has posted a 3.51 ERA in an even 100 innings since the trade deadline.How did that happen, and how meaningful can it be in a lost season?“They’re all here because they belong. They’re all here because they want to be here in the future,” interim manager Andy Green said before Friday’s 10-6 win over the San Francisco Giants. “They all have a lot of work to continue to do, but I don’t think you can look at it any other way but to be encouraged through the first month.”For the Mets, there have been two clear standouts over the last month: Nate Lavender and Daniel Duarte.Since making his major-league debut Aug. 4, Lavender has been the second-best reliever in baseball, according to FanGraphs’ wins above replacement, a touch behind Houston’s Josh Hader. In 12 2/3 innings over a dozen appearances, the lefty has yet to allow a run. Only eight men have reached base. He’s allowed one extra-base hit.Nate Lavender hasn’t allowed a run in his 12 2/3 innings of major-league pitching. (Caean Couto / Getty Images)“The biggest thing I’ve learned is to trust my strengths, to rely on the strengths that got me here,” Lavender said. “The job description is always the same: How can I get this guy out of the batter’s box?”The 29-year-old Duarte appeared in 36 big-league games before this season, most of them with the 2023 Cincinnati Reds. After bouncing between Triple A and the majors through the first half of the season, he’s been with the Mets since July 21.Duarte has allowed a run in just four of his 21 outings this season, and a recent rough stretch barely pushed his ERA over 2.00 on the year. His cutter/sweeper mix has kept the ball off opposing hitters’ barrels all season. He’s been almost untouchable to fellow right-handers, who are 4-for-37 off him this season.Late-season evaluations are notoriously tricky. That’s true for starting pitchers and position players, let alone the most volatile position in the sport. Combined, Lavender and Duarte have thrown 38 2/3 innings this season for the Mets. That’s the same number Frankie Montas threw for the Mets last season, and you don’t remember that happening.To Green, a reliever audition boils down to two key questions:• Does the stuff play at this level?• How does the pitcher handle the stress?The stuff sure looks as if it plays for Lavender, Duarte and others in that bullpen. And given the absence of just about anyone with high-leverage experience, they’ve handled plenty of potentially stressful late-game situations with aplomb.“For me, the two months give you a window into who they are,” Green said. “The thing about this game at the major-league level is you’ve got to show up again in spring training, you’ve got to show up again and do it in the season. You’ve got to keep showing up. The best relievers in the game show up year after year after year.“It’s not where you had a great August in 2026, and therefore you deserve to pitch here for the next three years. It’s not like that.”Regardless of how their bullpen performed down the stretch, the Mets were going to enter this winter in need of relievers. But the magnitude of that need looks different today than it did a month ago. Lavender and Duarte are not the only pitchers who have placed themselves on the radar for 2027. In Williams’ place, Kodai Senga looks salvageable as a reliever entering the final year of his contract. Dedniel Núñez has recovered from a rocky first few outings. Austin Warren hasn’t been optioned since April.“I know my stuff plays in the big leagues,” Warren said, “so it’s nice the organization notices that and gives me the chance.”Williams will return as the team’s closer, and Senga can now figure into the mix in some capacity. Reed Garrett and Tylor Megill are coming off Tommy John surgery. There will be choices, though not in every case options. Duarte and Warren will be out of minor-league options next season. (The Mets have been able to preserve Núñez’s option, since he went straight from the IL to a rehab assignment to the majors.)Warren pointed out that he’s thrown more innings in relief than any other active member of New York’s pen (“That’s a first,” he joked). But that bricolage of a bullpen has been one of the game’s best — and it’s becoming one of its tightest, too.“We love it,” Warren said. “All these guys deserve to be in the big leagues. Their stuff plays in the big leagues. I’m glad these guys got their chance, and we’re having fun, passing the baton every time.”“Success is contagious,” Lavender said. “Our bullpen has done a good job of picking each other up. And when you see someone go in and do the job well, you want to do the same thing.”