NEW YORK -- The Mets lost a key component of their lineup when Robinson Cano departed Sunday’s 5-2 win over the Brewers after taking a Gio Gonzalez fastball off his left hand. An X-ray administered at Citi Field were negative, but the Mets are concerned that the swelling in Cano’s hand might be hiding something worse. They will administer additional testing, including an MRI, on Monday once the swelling subsides.

“We’re still a little concerned,” Mets manager Mickey Callaway said. “The X-rays looked fine. But just who it is and where it is, I think we need to make sure that we’re doing everything we can, and dig deeper.”

Batting in the first inning, Cano took a first-pitch, 88-mph fastball off the back of his hand, near the left pinkie. It was the second time in eight days Cano had to depart after being plunked, though the first occasion was on his opposite wrist. Cano wound up spending one game out of the starting lineup as a result of that pitch.

This latest episode is likely also to cost Cano at least a game, though the Mets hope it’s not significantly worse than that. Their caution stems at least in part from a similar play last year involving catcher Kevin Plawecki, whose X-rays came back negative before an MRI revealed a hairline fracture in his hand.

“Anytime you have little bones in that area, it is [concerning],” Callaway said.

Cano was unavailable for comment after the game.

Juan Lagares replaced Cano as a pinch-hitter, as home-plate umpire Todd Tichenor ruled that Cano swung while attempting to move out of the way of the pitch. Lagares then moved to the outfield, with Jeff McNeil taking over Cano’s position at second base. If Cano misses any significant time, McNeil would replace him on a regular basis at second.

The Mets hope that is not the case. In 25 games, Cano was batting .270 with three home runs and a .754 OPS. He had recently caught fire as the Mets’ regular three-hole hitter, collecting multiple hits in six of his last 10 games entering Sunday’s play.

On the mend

Infielder Jed Lowrie, who sprained a left knee capsule in the early days of Spring Training, began a Minor League rehab assignment Sunday with Class A Advanced St. Lucie. He finished 0-for-4, playing both second base and shortstop.

The Mets have not indicated how long Lowrie will need to stay on assignment after missing the entirety of Spring Training because of his injury. Faced with similar circumstances earlier this month, Todd Frazier used up nearly the entire 20-day limit of his rehab stint. Even if Lowrie spends less time in the Minors, he’s likely looking at a mid-May Mets debut.

“We never put a timeline on it,” general manager Brodie Van Wagenen said. “We have been careful and deliberate with our rehab process for all of our guys, and want to progress him with the right amount of workload. We want to manage that carefully. The signs that we’ve seen so far have been very good.”