Jordan Montgomer of the Yankees hands the ball to manager Aaron...

Jordan Montgomer of the Yankees hands the ball to manager Aaron Boone as he leaves a game against the Mets in the third inning at Citi Field on Tuesday. Credit: Jim McIsaac

Few Yankees pitchers have been as consistent the last two seasons as Jordan Montgomery.

In the Subway Series opener Tuesday night, the lefthander didn’t come close to that level of quality in a 6-3 loss to the Mets.

Lasting just 2 1⁄3 innings, Montgomery was rocked for five runs (four earned) and five hits in his shortest outing of the season, allowing four of those runs in the bottom of the first, which quickly flushed the 2-0 lead he’d been given in the top of the inning.

All five of the hits went for extra bases, with two of them home runs.

TV cameras appeared to catch Montgomery, whose ERA ticked up to 3.50 from 3.24, asking Aaron Boone “Why?” upon being removed with one out in the third.

“I wanted to be out there, but I sucked, so obviously I needed to be pulled,” Montgomery said afterward.

Entering the night Montgomery had allowed three earned runs or fewer in 17 of his 19 starts this season — and three earned runs or fewer in 41 of his 49 starts since the beginning of the 2021 season — but it was evident early he would not be adding to those numbers in a positive way.

“I guess I was due a bad one,” Montgomery said.

Victimized often since 2021 by a lack of run support, Montgomery took the mound with a two-run lead.

That came courtesy of Aaron Judge’s 38th homer with one out in the first off Taijuan Walker and Anthony Rizzo making it back-to-back shots with home run No. 23. It marked the 14th time this season the Yankees hit back-to-back homers, five more than any other team in the majors. It also tied the club record for going back-to-back the most times, established in 2009.

Judge’s homer was his fifth in his last five games and eighth in his last 10 games. At that point, he had driven in 12 of the Yankees’ last 22 runs.

But after getting the lead, Montgomery blew up in a 33-pitch bottom half as the Mets stormed back.

After leadoff man Brandon Nimmo lined out, Starling Marte ripped a 1-and-2, 93-mph fastball down the leftfield line, his 10th homer making it 2-1. Francisco Lindor and Pete Alonso hit back-to-back doubles to tie it at 2.

Montgomery got Mark Canha looking, but Eduardo Escobar crushed a 1-and-0 sinker to left, his 12th homer giving the Mets a 4-2 lead. It marked the 15th homer allowed in 20 starts by Montgomery, with six of those homers coming in his last five starts, counting Tuesday’s. A Josh Donaldson throwing error in the third led to another run that made it 5-2.

“We’re not going to be perfect all year,” Montgomery said of a rotation that has been outstanding most of the season but has taken some lumps in the last month. “If you have 30 starts [in a year], you’re going to have five stinkers. Hopefully this is my one, and I’m just going to be right back to work tomorrow.”

Stanton to the IL

Giancarlo Stanton, who started in only two of the Yankees’ five games after the All-Star break, was placed on the IL Tuesday with left Achilles tendinitis.

The club backdated the stint to last Sunday, when Stanton said he was “fine” and Aaron Boone said he wasn’t too “concerned.”

“Yesterday [Monday], I got a call in the afternoon from our trainers and [they] said, ‘G requested an MRI.’ And I said, ‘On what?’ ” Boone said before Tuesday’s game. “His Achilles. He woke up and it was kind of really sore getting around. So he went and got it [the MRI]. It was right on the point he talked about, where he found the tendinitis. So hoping it’s a minor thing and we believe that, but that’s what changed [from Sunday].”

Boone said it was too soon to establish a time frame for Stanton, who is hitting .228 with 24 homers and an .807 OPS, to return, but the manager didn’t rule out a period of at least 2-3 weeks.

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