When the season began, Jose Iglesias was an afterthought, a veteran toiling in the minor leagues.

Now, he’s a critical piece to the Mets, made even more important with Francisco Lindor’s back injury that is likely to keep him out of this week’s series against the Nationals, if not longer.

Monday night was a first: Iglesias was starting at shortstop for the Mets.

This wasn’t new: He added to his clutch year by driving in the game-tying run in the eighth inning of his team’s 2-1, 10-inning victory, adding to his already impressive numbers with runners in scoring position (now 18-for-47 with 22 of his 25 RBIs.)

“The only thing that changes is my playing time. I have no room for rest. I’ve got to go up there with everything I’ve got,” said Iglesias, who is now riding a 10-game hitting streak. “And that’s what I’m here for. I’m just glad to do that. Like I said, I’m just trying to do my job and contribute to help this team all the way through.”

Before the game, manager Carlos Mendoza explained the decision to play Iglesias at shortstop.

Prospect Luisangel Acuna started there on Saturday and replaced Lindor at shortstop on Sunday in the second inning, but Mendoza wanted to get another left-handed bat in the lineup against Jake Irvin.

So he moved Iglesias to shortstop and started Eddy Alvarez at second base.

“He’s played shortstop pretty much all his career. I feel really good with him there,” Mendoza said. “Acuna is going to get playing time as well. We feel good with Alvarez at second base. Just playing the matchups as much as possible.”

The 34-year-old Iglesias has turned back the clock this season after spending all of last year in the minor leagues.

From the time he was called up on May 31, he has been a spark.

Iglesias has a slash line of .323/.372/.436 with a robust .808 OPS, which would be his best in his 12-year big league career.

The major question with Iglesias was his defense.

His range had diminished in recent years.

When the Mets didn’t bring him north after spring training, that was the reason.

“He’s worked so hard, and you got to give him the credit. You got to give credit to a lot of the people who helped him in the minor leagues, and continue to help him here,” Mendoza said. “It starts with the player. When we told him he wasn’t making the team out of spring training, it would’ve been easy for him to go home. He was like, ‘if I go to Triple-A, what do I need to do to get back?’”

It’s hard to imagine where the Mets would be without him.

Not only is Lindor now missing time, but Jeff McNeil was lost for the rest of the regular season due to a fractured wrist on Sept. 6. Iglesias went from a luxury to a necessity.