Less than a week ago, Jake Diekman was the hero of the Subway Series, striking out Aaron Judge. 

Now, he’s out of a job. 

The Mets designated the struggling left-hander for assignment on Monday in a somewhat surprising move.

In his place, they called up fellow southpaw Matt Gage. 

Diekman failed to build off his save against the Yankees, allowing runs in each of his last two outings and had a 10.80 ERA in July. He never could get his walks under control, issuing 24 in 32 innings pitched that contributed to an unsightly 5.63 ERA. 

“Not an easy one, especially when you’re dealing with a guy like Diekman, who’s been here since Day 1 — spring training, here all the way to this point, been in this league a long time,” manager Carlos Mendoza said before the Mets opened a three-game series against the Twins at Citi Field. “He was such a professional. He was always willing to take the baseball. When it was hard for him during his struggles, he was always available, he always wanted to be here. But we got to a point where we needed to make a decision. We decided to go that route.” 

The Mets signed Diekman in the offseason to a one-year deal for $4 million. There was a vesting option that if he appeared in 58 games, he would be under contract for next season at another $4 million.

He wound up making 43 appearances for the Mets. 

The 31-year-old Gage was picked up from the Dodgers in exchange for cash considerations on July 7.

He pitched well for the Astros last year in limited duty, notching a 2.70 ERA in 6 ²/₃ innings.

This year for Triple-A Oklahoma City and Syracuse, he had a 3.42 ERA in 26 ¹/₃ innings with 34 strikeouts. Gage joins Danny and Alex Young as left-handers in the bullpen.

Alex Young, picked up off waivers from the Giants, has been impressive in a short sample size. He has yet to allow a run in 4 ²/₃ innings while striking out five and giving up just one hit. 

“The changeup plays, and the arm action, it’s the same whether it’s the fastball or the changeup, and his ability to throw [either pitch] at any time throughout an at-bat in any situation gets swings and misses or ground balls as well,” Mendoza said. 

The only original members of this year’s bullpen are now Edwin Diaz and Adam Ottavino. Drew Smith and Brooks Raley were lost to season-ending injuries.

Diekman, Michael Tonkin, Jorge Lopez and Yohan Ramirez were all designated for assignment.

The Mets are hoping to get back injured relievers Sean Reid-Foley and Reed Garrett soon. They have added relievers Phil Maton and Ryne Stanek in trades recently as well. 

“I think every team goes through that, and we’ve dealt especially with injuries,” Mendoza said. “We had a lot of guys who made the Opening Day roster get hurt. It always happens, it’s always evolving, you’re always looking for the next guy and how can you get better. But it’s been a little bit of a challenge to be honest with you.”