The Mets might be forced to begin a three-game series against the Nationals on Monday night without one of their most dangerous bats.

Curtis Granderson missed Sunday’s 7-1 loss to the Phillies with what he called muscle discomfort in his right hip. After initially feeling symptoms Saturday, Granderson, 36, couldn’t prepare himself to pinch hit Sunday.

“I tried to get ready to hit and I just didn’t feel right hitting,” said Granderson, who has a .234 average, 12 homers and 34 RBIs.

After stumbling out of the starting gate this season, he has been one of the Mets’ most productive bats. Granderson has homered five times in his last 10 games and ranks in the top 10 in the National League since May 1 in slugging (.596) and on-base percentage (.403).

While the Mets have been ravaged by injuries, he has been a reliable presence, playing in 77 of the team’s 81 games. Only Jose Reyes has appeared in more games.

“He came in this morning — and if there’s one thing Curtis Granderson never does, it’s complain — and said ‘my hip is a little tight,’ which means it’s tight,” manager Terry Collins said before the game. “So he’s off.”

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Brandon Nimmo went 0-for-4 while leading off and playing centerfield for Granderson, who spent the game getting treatment.

Granderson felt pain and discomfort while finishing off his swings Saturday, though he couldn’t pinpoint whether it began on a specific play or at-bat. He even reviewed video but has no idea how he hurt himself.

“It was kind of weird,” he said. “I was going through the game and everything felt fine. I noticed a little something, but nothing too crazy.”

The symptoms only worsened, making Granderson’s availability a day-to-day proposition as the Mets enter their final six games before the All-Star break.

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