Seth Lugo, Robert Gsellman embracing their versatility

Seth Lugo and Robert Gsellman hear the starter-versus-reliever debate revolving around them, and they have been consistent but professional in their preferences. They would rather be in the rotation. But they also wonder if this can be about more than their seasons or the Mets, if they can help change baseball and pitching and the way baseball thinks about pitching.

What if being a swingman, relief ace or utility pitcher — or any mixture of those — was a desirable goal?

“We’ve talked about it since spring training, the first week of the season, even now — we try to set ourselves aside from bullpen/starter,” Lugo said. “We both want to be versatile, pushing each other to make it a respectable role that people wouldn’t mind doing (if) they see guys like us, or like (Cleveland’s) Andrew Miller or something, take on something like that. An established role that we want to be a part of. We want to help lead the way as far as baseball changing and pitchers pitching in different scenarios, different situations.”

By virtue of their effectiveness as relievers — and the Mets’ full rotation picture for 2019 — Lugo and Gsellman might get the chance to keep proving themselves versatile. The bullpen, for now filled with a lot of rookies, is a massive question mark for next year.

The Mets began this season with a grand four-piece plan for the back end: Jeurys Familia, the onetime All-Star closer; AJ Ramos, the other onetime All-Star closer; Anthony Swarzak, the offseason addition; and Jerry Blevins, the lefty specialist.

So much for that. Familia’s Mets career ended with a trade last month. Ramos’ season ended with shoulder surgery in June. Swarzak has been hurt three times and mostly ineffective when healthy. And Blevins has been bad against lefties (but good against righties). Of that quartet, only Swarzak is under contract for next year.

That leaves the Mets with two primary options as they begin to plan for 2019, when they say they expect to contend: Build a bullpen mostly from scratch (an endeavor fraught with risk), or keep Lugo and Gsellman as relievers and use them as building blocks for a new back-end core.

The latter is tempting.

“You know going into the offseason that that’s an option,” manager Mickey Callaway said. “You can try to build or acquire players based on that.”

“The good thing is we have the flexibility to use them to help us win games in either role and glad they both can get the job done.”

Lugo (2.86 ERA) in particular has filled that flexible utility-pitcher role this season. He is one of only two hurlers in the majors with at least five starts, at least five holds and at least one save. (The other: Tampa Bay’s Sergio Romo, who has made five starts as an “opener,” going a combined 4 2/3 innings.)

Gsellman has been used exclusively in relief and taken to it well, posting a 3.57 ERA. He struggled in May and June (5.40 ERA), but has paired a bit more rest of late and a tweak to his arm slot into newfound effectiveness. “Get over the top, get that good sink,” Gsellman said. He hasn’t allowed a run this month.

A return to the rotation remains Gsellman’s goal. But if a longer-term bullpen assignment is his fate?

“That’s fine,” he said. “I know we have great arms up front in our rotation — and they can take us real far. If we can close it down in the back end of the bullpen, I think we’d have a great chance and we’d be a great team.”