Despite being one of the weakest teams in MLB, the Pirates had a shot at beating the Mets on Monday night thanks to their pitcher’s standout performance for the first six innings.

Then Paul Skenes departed.

And the Mets, as has been their modus operandi this season, rallied in the late innings against an underwhelming bullpen.

In the seventh inning, the Mets managed to score two runs, and although they had a bit of a scare in the ninth, they secured a 4-3 victory with Pete Alonso delivering a walkoff sacrifice fly against David Bednar.

The winning rally was kickstarted by Francisco Lindor, who got on base due to Isiah Kiner-Falefa’s fielding error, followed by Juan Soto’s single that advanced Lindor to third base. The game was then sealed when Alonso hit a deep fly to right field.

Lindor’s fielding error had helped the Pirates tie it 3-3 in the ninth after Huascar Brazobán allowed a leadoff single. Ke’Bryan Hayes’ shot off Luisangel Acuña’s glove brought in the run before Brazobán got Bryan Reynolds to hit into an inning-ending double play.

Skenes, last season’s NL Rookie of the Year, allowed one run over six innings and departed at 92 pitches, after the Pirates went ahead 2-1.

But the Mets tied it against lefty Caleb Ferguson before Acuña alertly raced home from second on Alonso’s shot off the third baseman Hayes’ glove. Acuña narrowly averted Joey Bart’s tag at the plate, reaching in with his hand, to give the Mets their margin of victory.

Bart led off the eighth against Dedniel Nunez and hit a shot to left field that Nimmo grabbed above the fence to preserve the lead.

David Peterson nearly matched Skenes’ sharp performance by allowing two earned runs on five hits with seven strikeouts and three walks over six-plus innings.

Peterson survived two walks in the first inning before allowing a homer to Kiner-Falefa leading off the second. Kiner-Falefa, before the game, received a charcoal portrait of his cousin Ralph Kiner from the legendary Mets broadcaster’s son Scott.

It was Kiner-Falefa’s first time meeting a member of Kiner’s immediate family.

Jeff McNeil stroked an RBI double in the fourth that tied it 1-1.

Nimmo doubled leading off the inning before McNeil delivered against Skenes with one out. But Francisco Alvarez and Brett Baty were retired in succession to end the threat.

Hayes singled with two outs in the fifth, but Peterson escaped by striking out Reynolds. Peterson, following Kiner-Falefa’s homer, retired 10 straight batters before Jared Triolo doubled in the fifth.

Andrew McCutchen and Kiner-Falefa each singled in the sixth, but Peterson retired Alexander Canario to keep it at 1-1.

The Mets wasted an opportunity in the sixth, as Alvarez hit into an inning-ending double play after Mark Vientos doubled and McNeil walked.

Peterson was removed after walking Triolo to start the seventh.

José Buttó was charged for a disengagement violation that moved Triolo to third and after Hayes walked, Reynolds’ RBI fielder’s choice gave the Pirates a 2-1 lead.

Ferguson drilled Tyrone Taylor leading off the bottom of the inning. Taylor stole second and reached third on Acuña’s infield single. Soto’s ground out tied it 2-2.

Alonso’s single off Hayes’ glove against Colin Holderman gave Acuña the runway he needed to score the go-ahead run.