DETROIT — Any chance for a late-inning comeback by the Mets went straight to Hel-sley in a span of three batters on Wednesday.

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Ryan Helsley’s nightmare to begin the bottom of the seventh inning at Comerica Park: Single, walk, home run. And for a second straight outing, an early hook was attached to the right-hander without completing an inning.

The beleaguered reliever was part of an overall disappointing bullpen performance in the team’s 6-2 loss to the Tigers that denied the Mets a three-game sweep.

Kerry Carpenter delivered the damaging blow with a three-run homer on a 100 mph heater from Helsley, who had entered with the Mets behind 3-2. Two innings earlier lefty reliever Gregory Soto had allowed two inherited runners to score.

It was just the latest letdown by Helsley, a former All-Star closer with the Cardinals who has pitched to an 11.45 ERA in his 14 appearances since arriving at the trade deadline. In only five of those appearances has Helsley worked a scoreless inning.

“It feels like guys are swinging at 100 [mph] like it’s 91 right now,” Helsley said. “When you feel like you have to be perfect out there it’s not a good thing.”

Helsley has expressed a belief lately that pitch-tipping is sabotaging him. Mechanical adjustments have followed, but not the results.

As much as manager Carlos Mendoza might hope to find lower-leverage spots for Helsley, burying him in the bullpen isn’t an option.

“We acquired this guy, and we believe in this guy,” Mendoza said. “In order for us to get where we want to get, we are going to need him. It’s obviously hard for him right now and for all of us, but we have got to get him right.”

Clay Holmes, a former reliever who went through his ups and downs as Yankees closer — he was removed from the role late last season — can certainly understand Helsley’s situation.

“I have been traded in midseason and I have been a closer,” Holmes said. “There’s a lot that goes to all this stuff, especially moving teams, moving roles and you’re in a playoff chase. There’s a lot that goes on there.”

After scoring a combined 22 runs in winning the first two games of the series, the Mets were contained offensively against Casey Mize and the Tigers bullpen.

Next stop is Cincinnati for three games against a Reds team that desperately needs to sweep the Mets to keep their fading wild-card hopes alive. The Mets began the day with a five-game lead on the Reds for the NL’s third and final wild card.

Holmes rolled into the fifth, but after walking two batters was removed at 88 pitches. Both runners scored with Soto pitching, after Holmes departed. Overall, Holmes allowed three runs, two of which were earned, on five hits with three walks and six strikeouts over 4 ²/₃ innings.

Holmes surrendered an RBI single to Jake Rogers in the second that put the Tigers ahead 1-0. Zach McKinstry’s single and a catcher’s interference by Hayden Senger with Javier Báez at the plate led to the run. Holmes walked Spencer Torkelson leading off the frame, but he was thrown out by Jeff McNeil in center attempting to advance on Wenceel Pérez’s fly out.

Pete Alonso stroked an RBI double in the third that tied it 1-1. Francisco Lindor doubled leading off the inning against Mize before Alonso delivered for his 113th RBI this season.

Holmes walked two batters in the fifth and was removed with two outs. Gregory Soto unleashed a wild pitch that moved the runners to second and third before Riley Greene’s two-run single — a one-hop shot that eluded Lindor’s glove — put the Mets in a 3-1 hole.

Mark Vientos’ RBI single in the sixth got a run back for the Mets, but with the bases loaded Starling Marte grounded into an inning-ending double play. Juan Soto’s walk and Alonso’s infield single started the rally.

“Every game matters, and we’re trying to win here,” Lindor said. “But winning this series was also important.”