As Luke Voit went down swinging at a Taylor Clarke slider in the third inning of Tuesday’s game, Yankees manager Aaron Boone noticed something might be off.

Maybe it was Voit’s grimace, or the way he walked to first base for the top half of the fourth. Whatever the case, Boone’s instinct proved right.

Voit left the game in the top of the fifth with a core muscle injury, and by the end of the night he was undergoing an MRI exam, the Yankees announced.

This injury didn’t happen at one moment, Boone said, at least not that he could point to.

“Even in talking to Luke during the game when he was coming out, he was having a hard time putting his finger on it,” Boone said. “He just said, ‘I was having a hard time getting loose, before the game and all game.’ Like he didn’t feel like he did anything to it.”

Boone, leaning back in his chair and gesturing to his core to emphasize the point, said Voit indicated something in his core just felt off.

What makes this particularly scary for the Yankees is Voit has already dealt with a core injury this season, missing seven games after experiencing tightness in his abdomen during the Red Sox series in London. He was removed from a game then after running out a double. Though it’s unclear whether this injury is directly related, it’s certainly a red flag.

“It wasn’t the normal, when a guy does something in a course of a game that injures something,” Boone said. “There didn’t seem to be anything like that.”

Tyler Wade replaced Voit in Tuesday’s 4-2 loss to the Diamondbacks, playing third base as Gio Urshela moved to first. Wade, just recalled from Triple-A Scranton/Wilkes-Barre on Monday, accounted for half the Yankees’ offensive output on the night with an eighth-inning solo home run.

When Voit missed time before the All-Star break, the Yankees turned to Mike Ford, Edwin Encarnacion and DJ LeMahieu to play first base. LeMahieu, the logical choice to play first should Voit miss extended time, missed Tuesday’s contest with a tight groin. Boone didn’t say postgame whether LeMahieu would play Wednesday, but framed the decision as mostly a matter of caution.

“DJ’s doing well,” Boone said. “Just trying to be wise here as we avoid this IL thing, especially with an off day coming [on Thursday].”

Replacing Voit seems a relatively simple proposition thanks to the Yankees’ depth, but he is an important piece of the offense. Before Tuesday’s game, he was slashing .279/.391/.494 — good for an OPS+ of 136, behind only Aaron Judge and LeMahieu among the Yankees’ everyday players. He’s also third on the team in home runs with 19. Losing him for any period of time would give them another obstacle to overcome, even if it wouldn’t create an urgent need to deal for a first baseman by Wednesday’s 4 p.m. trade deadline.

While the Yankees were in the clubhouse mourning the loss, though, Voit was still undergoing tests, and the most Boone could offer of his status was,

“We’ll just have to wait and see.”