The loss of JD Martinez would be significant for the Mets’ struggling offense.

The club’s designated hitter was taken out of the game after his only at-bat on Tuesday ended with a 99.6 mph fastball hitting his left elbow and causing a bruise.

In the second inning of the series opener against the A’s at Citi Field, Martinez worked his way to a 2-2 count before taking the pressure on the defense and almost jogging toward the visiting team as if he wanted to run away from the pain.

Coach and manager Carlos Mendoza looked for Martinez, who stayed in the game to run the bases and then scored.

But Martinez sat with a coach on the team bench, briefly held him by the elbow and then disappeared into the tunnel.

One inning later, Mark Vientos was used as a pinch hitter for Martinez when it was his turn to pitch.

Martinez entered his first 87 games with an OPS of .779 and 12 home runs.

Like most of the club, he has struggled recently, entering his last seven games with 3-of-24 hits and 10 strikeouts.