MILWAUKEE – Just as the Mets were preparing to “Roll out the Barrel” for another post-game celebration, disaster struck in the eighth inning.

Phil Maton came in to protect a one-run lead, and by the time he left after the third out, the Brewers had hit two home runs and redirected the momentum in this NL Wild Card Series.

There will be a decisive Game 3 on Thursday, after the Mets lost their chance for a two-game sweep in this series with a 5-3 loss in front of 40,350 at American Family Field.

This wasn’t just Maton’s fault: the Mets went the last seven innings without scoring.

But the right-hander was jumped almost from the moment he entered the game, and the Brewers went for the kill.

Garrett Mitchell’s two-run homer with two outs was the breaker, after rookie Jackson Chourio’s blast (his second of the game) erased the Mets’ 3-2 lead.

It was a second shaky performance in a row by Maton, who had to be replaced in the eighth inning by Edwin Diaz in Atlanta on Monday.

On this night, Reed Garrett and Ryne Stanek each gave the Mets a scoreless inning in relief before Maton collapsed.

Sean Manaea gave the Mets five innings, allowing two earned runs on six hits and striking out four. The left-hander was removed after 86 pitches with the Mets leading 3-2.

Brandon Nimmo hit an RBI single in the first inning to give the Mets a 1-0 lead.

Francisco Lindor led off the game with a walk and Jose Iglesias avoided a double play with a sprint to first base that just beat the relay throw before Mark Vientos reached on an infield hit and delivered Nimmo with a helicopter through the first base gap.

But the Mets rally was cut short when Pete Alonso tripped over his bat while running to first base on a grounder that became an easy 6-4-3 double play.

Chourio got the run back with a homer to lead in the bottom half of the inning.

Manaea threw an 0-2 sinker that Chourio blasted over the right-field fence.

The Mets jumped on Frankie Montas again in the second, scoring two unearned runs after Montas dropped Rhys Hoskins’ throw while covering first base on a grounder by Starling Marte.

Then, after Tyrone Taylor singled, Francisco Alvarez hit an RBI single. Lindor’s ensuing sacrifice fly gave the Mets a 3-1 lead.

Montas lasted only 3 ²/₃ innings and gave up three runs, two of which were unearned, on six hits and one walk with three strikeouts.

Trevor Megill defeated Nimmo with two outs in the fifth, sending the runner to second base, but struck out Alonso. Megill, the older brother of Mets pitcher Tylor Megill, struckout three batters in the inning.

The Brewers scored for a run in the fifth to pull within 3-2.

Brice Turang hit a leadoff double past third base and advanced on Chourio’s groundout to the right side before Blake Perkins’ drive to center brought in Turang.

The Mets loaded the bases in the sixth against Joel Payamps, who struck out Iglesias to end the threat. JD Martinez walked and Marte singled before Lindor was walked intentionally with two outs.

Garrett allowed a single to Gary Sanchez in the sixth, but his pinch runner, Mitchell, was nailed by Alvarez in an attempt to steal second.