PORT ST. LUCIE, Fla. -- As some of Mark Vientos' teammates prepared for their final Grapefruit League game in Port St. Lucie, and many of the rest traveled to Jupiter, Fla., for the other half of a split-squad game, Vientos’ locker at Clover Park stood mostly empty on Sunday morning. Mets officials gave Vientos the day off after telling him, in a bit of a late-spring surprise, that he would not make the Opening Day roster.

“Obviously, he wasn’t happy, and we expected that,” manager Carlos Mendoza said. “It’s something that, as a player or as a manager, you don’t want anybody happy when they get the news that they’re going back to the Minors.”

• Split squad box scores: NYM 10, WSH 1 | MIA 5, NYM 1

For nearly all of Spring Training, Vientos was an obvious pick to make the Mets. A former top prospect who could conceivably play a role for years to come, Vientos had the backing of team officials who wanted to see him in an expanded everyday role. But then J.D. Martinez’s price dropped, the Mets signed the six-time All-Star a week before Opening Day and Vientos found the floor ripped out from under him.

• Martinez eager to provide Mets with leadership, power

Although New York still could have carried Vientos as a fill-in until Martinez was ready, they instead chose to option him to Triple-A Syracuse and give the job to Zack Short.

“As we looked at our roster construction, looked at some of the matchups earlier in the season, we just thought this made the right sense, both for him from a playing-time perspective,” president of baseball operations David Stearns said, “and for our team at the Major League level.”

Specifically, Stearns said, the Mets want Vientos to continue improving defensively; he’ll receive that opportunity as the everyday third baseman at Syracuse. Offensively, the club does not consider Vientos a finished product.

The conversation came as unwelcome news to Vientos, who led the Mets with five Grapefruit League homers after slashing .211/.253/.367 in sporadic playing time last season as a rookie. But it is not the end of his story.

“The Opening Day roster is just the roster for one day,” said Brett Baty, the starting third baseman and one of Vientos’ close friends on the team. “The amount of players a team goes through over a full season has got to be close to 70. So we’ll see him very soon. He’s one of the best hitters, players, that I’ve ever played with. He’s one of the hardest workers. So he’s going to go down there and rip as hard as he can.”

With Vientos in the Minors, Stearns and Mendoza have two roster decisions still to make:

Final bench spot
The Mets will take only 13 position players north with them, which is the same number they’ll have on the Opening Day roster. Twelve have been told for sure that they’re making the team. The 13th, DJ Stewart, is on the roster bubble.

If nothing else happens between now and Thursday, Stewart will make the team as a left-handed backup outfielder and first baseman. But the Mets are still canvassing the waiver wire to see if any players they wish to acquire come available. As such, they haven’t guaranteed Stewart a job.

One other candidate, Ji Man Choi, was told Sunday morning that he won’t make the club. Choi declined to exercise the opt-out clause in his contract, according to a source, and will report to Triple-A Syracuse.

Final two bullpen spots
Fourteen pitchers, conversely, will head to New York, but only 13 will make the Opening Day roster. The final two bullpen spots will go to some combination of Michael Tonkin, Sean Reid-Foley and Yohan Ramírez.

Tonkin remains a heavy favorite for one of those jobs, partially because of his sparkling Grapefruit League campaign -- he didn’t allow a run over 7 2/3 innings -- and partially because his “stuff package,” as Stearns called it, is unique among Mets relievers. His low three-quarters arm slot gives hitters a different look.

If Tonkin makes the team, that leaves one spot for either Reid-Foley or Ramírez. Both are out of Minor League options and must be exposed to waivers if they don’t earn a spot. Both have also been popular with scouts who watched the Mets this spring. Stearns will likely spend the next few days engaging clubs on potential trades before making a final decision.