Robert Gsellman of the Mets throws a pitch during a spring...

Robert Gsellman of the Mets throws a pitch during a spring training game against the Nationals at The Ballpark of The Palm Beaches on Sunday in West Palm Beach, Fla. Credit: Getty Images/Eric Espada

JUPITER, Fla. — Among the Mets’ agenda items in these final days of spring training: Figure out who will be in the bullpen.

There is at least one spot — and potentially several spots — up for grabs. The season-opening group won’t necessarily include all of the mainstays from the recent past.

"Spring training camp is all about competing," manager Luis Rojas said. "We’re considering everything. We’re staying open-minded about everything."

Well, surely not quite everything. Let’s not confuse spring training silly talk with realistic roster choices. The Mets have several bullpen locks, even with Seth Lugo (right elbow surgery to remove a bone chip) out for the first month or so.

Who are the locks?

Closer Edwin Diaz isn’t going anywhere. Neither is Miguel Castro, who allowed his first hit in six exhibition appearances Wednesday. Trevor May and Aaron Loup have guaranteed contracts (signed over the offseason). That is four of a likely eight relievers.

"Those guys you expect to be part of that [late-inning] mix," Rojas said.

Who makes up the other half?

Jeurys Familia and Dellin Betances also have guaranteed contracts but have struggled in recent seasons and during spring training. Robert Gsellman, who can be sent to the minors without his consent, is at risk of not making the team. And the eighth reliever is TBD.

"He’s competing to win [a bullpen job]," Rojas said of Gsellman. "He can be a great asset for us in the bullpen if he makes the team."

Gsellman is third on the Mets with 126 appearances in the past three seasons, right behind Lugo and Familia (131 each). However, he also had a well-below-average 4.91 ERA in that span.

The Mets have raved for years about Gsellman’s "stuff" — how good a pitch is — but that hasn’t translated into results.

"Having his identity is important, knowing what type of a pitcher he’s going to be," Rojas said. "He’s been a sinker/slider guy. I think he’s pursued [being] a four-seam/curveball guy. So to know the identity of which guy you’re going to be and stick to those strengths is very important for him. I think those are some of the conversations he’s having with [pitching coach Jeremy] Hef[ner]."

What’s up with Familia and Betances?

They are more likely to make the team because of the Mets’ financial commitment. Familia is due $11.67 million this season, Betances $6 million. Teams rarely cut players with those kinds of salaries at this time of year.

But both have had problems during camp. Familia is up to seven walks in six innings, though he has limited opponents to just one earned run. And Betances has shown no hint of improved velocity as spring training has progressed, a dynamic he and the Mets have been talking up for 13 months. His fastball was mostly in the low 90s on Wednesday against the Cardinals.

That’s probably not enough to cost him his job, though.

"This is a guy that I think at this point, you gotta say that he’s part of our bullpen," Rojas said.

Betances will continue trying to figure out how to pitch without his high-90s heat of years past. The solution involves a lot more homework.

"I’ve got to be able to read swings, pay a lot more attention to scouting reports on what certain guys like to do, what pitch is better," Betances said. "Pay more attention to detail than I did in the past."

Who gets the job(s)?

It looks like one spot if the Mets keep Gsellman in the majors, two spots if they don’t (and three spots if the Mets opt for nine relievers).

Jacob Barnes, who is on the 40-man roster and cannot be optioned to the minors, has impressed Mets officials and has the ability to throw multiple innings, something the club values. Mike Montgomery could serve as a long reliever and a second lefthander (alongside Loup); he is able to opt-out of his contract to seek a major-league gig elsewhere if the Mets don’t add him to the roster by some point this weekend.

There are alternatives, though.

"It's a complicated question right now, still," Rojas said, "even though we're [four] games away from finishing the spring-training schedule."

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