NEW YORK -- After throwing his sixth pitch of the game on Thursday night at Citi Field, D-backs right-hander Zac Gallen motioned for catcher Gabriel Moreno to come out to the mound.

Moments later, Gallen walked off the field with one of the team’s athletic trainers.

It was the beginning of what would prove to be a bad night for the D-backs, who not only dropped their fourth game in a row -- this one by a 3-2 margin to the Mets -- but had to put their ace pitcher on the injured list with a right hamstring strain.

Here’s what you need to know about the injury.

It actually happened on the pitch before his final pitch of the night
Gallen exited after throwing a first-pitch ball to D.J. Stewart, but he said he felt it on the pitch before that which was lined to left-center for a single by Francisco Lindor.

“Just hamstring grabbed on me,” Gallen said of the pitch to Lindor. “So [I] threw another pitch to see if it was severe in the sense of if I could keep pitching or not.”

This is not his first issue with the hamstring this year
Gallen exited his April 26 start against the Mariners with what the team called at the time tightness in his right hamstring. After the game, he said it felt almost like a cramp, and the team felt good enough about it that he did not receive an MRI.

In fact, Gallen had been scheduled to pitch five days later, but he ended up getting skipped due to a confluence of events that included a game delayed two hours due to a beehive on the backstop.

This injury appears to be a little different
While it’s the same hamstring that is causing Gallen problems, it seems like this injury might be more severe. First is the fact that the team immediately listed it as a “strain” instead of mere tightness like in Seattle.

“A little bit different,” Gallen said. “The one in Seattle was a little bit more minor. This one is mild, I guess. It felt similar to what it did in 2021. I don’t really know the scale [of it], I just knew that I just couldn’t keep going or I would put the team in jeopardy of not giving them a chance to win.”

Gallen had a hamstring injury in 2021
In his quote, Gallen likened this feeling to the one he had in 2021, when he strained his hamstring on July 2 against the Giants at Chase Field.

That injury forced the right-hander to miss 15 days, which he said he is hoping is the worst-case scenario this time around.

Gallen did feel a little something in the hamstring two starts ago
While pitching against the Tigers on May 18, Gallen said he felt a little cramp in his right hamstring early in the game but was able to pitch through it without any other issues. In his start against the Marlins last Friday, he didn’t have any issues in his seven innings of work, and other than being aware of the hamstring situation, he did not do anything special.

“Just thought maybe it was a cramp issue,” Gallen said of the game against the Tigers. “Just kind of maybe overactive muscles and whatnot in the leg. So it kind of felt like I was in a good spot, training staff felt like I was in a good spot. Like I said, my routine was pretty stock standard for what I normally do.”

Losing Gallen would be another blow for the D-backs
The D-backs have been decimated by injuries this year. On the position player front, shortstop Geraldo Perdomo and outfielder Alek Thomas have missed most of the season.

As for the rotation, Arizona lost left-hander Eduardo Rodriguez to a left lat strain during Spring Training, and he has yet to throw a pitch this year. Co-ace Merrill Kelly has been out with a right shoulder strain since April 20.

“I think we're all heartbroken over Zac,” reliever Ryan Thompson said. “That's a real tough blow. I'm not sure what's going to happen with that, but we’ve got to pull together. I mean, this is a team sport, and it's been tough, but we're going to come tomorrow ready to do what it takes.”