NEW YORK — The radar gun at Citi Field will be putting in some overtime Wednesday night.

With Mets ace Jacob deGrom and his 102 mph fastball on the hill, the Cubs are countering with a flamethrower of their own in Robert Stock.

The 31-year-old right-hander will make his first appearance of the 2021 season Wednesday night to fill a hole in the Cubs rotation.

Down with Triple-A Iowa, Stock has been lighting up the radar gun, touching 101 mph and reportedly holding it into the 4th inning of outings.

“He’s been throwing good,” David Ross said. “Been starting some games, been attacking hitters, getting after guys, throwing strikes. Obviously he throws hard. They said he was the best guy suited, was throwing really well and was a good guy to fit in for tomorrow.”

Stock last pitched on June 8 and struck out 5 batters in 4 innings while allowing a run for Triple-A Iowa.

In all, he has a 4.12 ERA and 1.07 WHIP in 9 appearances this season while striking out 25 batters in 19.2 innings.

“I got a nice text from [Iowa manager Marty Pevey] that said he’s throwing the ball really well and competing and we would love him,” Ross said. “But that is the Triple-A assessment. We’ll wait and see how everybody does when they get up here. It’s a lot of decks up here that change people.

“Rob’s been in the big leagues before, so I’m excited about seeing what he’s got to offer.”

Stock has 52 career MLB games under his belt — all as a reliever. He had a 2.50 ERA in 39.2 innings in 2018 with the Padres but had some trouble with control in 2019-20 in San Diego and Boston (6.8 BB/9).

The Cubs selected him off waivers in December from the Red Sox.

Stock is filling in for a Cubs rotation that is currently missing Trevor Williams (appendectomy) and Adbert Alzolay (blister). Williams is slated to see a doctor later this week to get the all-clear to ramp up his intensity while Alzolay threw a light bullpen Monday.

The Cubs are anticipating Alzolay will throw another bullpen in the next few days and will evaluate his timeline after that point. He is eligible to return from the IL Friday but will likely be at least a couple days behind that.

“He’s progressing well,” Cubs pitching coach Tommy Hottovy said. “The last thing we want to do is rush it back. I think we’ve stress-tested it enough but not to a full game mode. Until we do that, then we’ll have a better assessment.”

On the topic of injured pitchers, the Cubs still don’t have an idea of when relievers Rowan Wick (side) and Jonathan Holder (shoulder) might be able to join the big-league bullpen.

Both right-handers are currently in throwing programs but have not yet tossed an official bullpen.

Wick has been dealing with this side/oblique injury for nine months after walking off the mound Sept. 16 at Wrigley Field with pain in his left side. He has seen multiple doctors and received different opinions but still cannot shake the issue fully.

The 28-year-old has been a big part of the Cubs bullpen the last two years with a 2.66 ERA, 10 holds and 6 saves. His recovery from the strange injury has been slow but the Cubs hope he can come back and help the team late in the season.