Mets outfielder DJ Stewart during a spring training workout on Feb....

Mets outfielder DJ Stewart during a spring training workout on Feb. 19 in Port St. Lucie, Fla. Credit: Newsday/Alejandra Villa Loarca

The Mets’ initial reaction to having to wait for J.D. Martinez to join the team was to tell DJ Stewart on Wednesday that he had made the Opening Day roster.

Manager Carlos Mendoza announced that Stewart, a lefthanded-swinging outfielder/first baseman/designated hitter, is the final position player for the 26-man roster that will face the Brewers in the season opener.

Stewart’s hold on a job could be tenuous, however, as the Mets will have to make room for the veteran Martinez in about 10 days to two weeks. Martinez will become the team’s everyday DH when his mini-spring training ends.

Mendoza said Martinez is at the Mets’ minor-league camp in Port St. Lucie, Florida, and is getting multiple at-bats per day. On Wednesday, the 36-year-old got six against righthander Adrian Houser, the starting pitcher who also stayed back to get some extra work in before he makes his first Mets appearance on Tuesday against Detroit.

Mendoza said the Mets will decide after a week or 10 days whether Martinez — who signed a one-year deal on Saturday — will need at-bats with one of the club’s minor-league affiliates or will continue to get ready in Port St. Lucie.

The Mets have one more roster decision to make before the opener. They have two bullpen spots for three candidates: Michael Tonkin, Sean Reid-Foley and Yohan Ramirez. All three are righthanders.

Senga throws . . . again

Kodai Senga played catch in the outfield during the Mets' Citi Field workout. But it wasn’t the first time he has done so since the Mets cleared him to throw.

Mendoza said Senga’s first time throwing since he was shut down with a shoulder strain was on Monday in Port St. Lucie, while the Mets were across the state playing the Yankees in Tampa.

Mendoza said Senga is progressing nicely. The righthander is expected to miss at least the first six weeks of the season.

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