Rafael Montero’s jersey was hanging in the Mets locker room last night. But the righthander will not be activated until Wednesday as the Mets add an extra arm for their weary bullpen before their matinee against the Marlins.

Montero was on hand Tuesday night just in case the Mets needed to use Logan Verrett in relief, which would have meant a start for Montero. They didn’t use Verrett, so he will start as scheduled in place of the injured Jacob deGrom.

DeGrom is still on the active roster even though he left the team Monday to fly to Florida, where his wife, Stacey, gave birth to the couple’s first child. Jaxon Anthony deGrom arrived at 9:23 p.m.

The Mets could place deGrom on the paternity leave list and add a player. But deGrom is also sidelined with a strained lat muscle, which is why Verrett was tapped to spot start Wednesday to begin with.

What the Mets are concerned about is losing deGrom for even longer. If they place him on paternity leave and then have to put him on the 15-day disabled list because his injury isn’t healing fast enough, they won’t be able to back-date him to Wednesday for the DL stint.

So the Mets optioned Eric Campbell to Las Vegas after the game instead to make room for Montero.

n Extra bases

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Zack Wheeler had a procedure to remove a suture knot from his right forearm which had been causing skin irritation. The procedure is not expected to delay his expected midsummer return from Tommy John surgery . . . Jerry Blevins allowed his first baserunner as a Met on Monday when Dee Gordon singled with two outs in the ninth. Blevins had retired 21 straight dating to last April. He missed most of last season with a fractured left arm.