Mets pitcher Kodai Senga, center, and free agents Jordan Montgomery,...

Mets pitcher Kodai Senga, center, and free agents Jordan Montgomery, left, and Blake Snell. Credit: Newsday / Alejandra Villa Loarca; AP / Tony Gutierrez; Kathleen Malone-Van Dyke

TAMPA, Fla.— The Mets’ sales pitch seemed to be working.

People were warming to the idea of forgiving the winter’s fiscal restraint, dreaming on the young prospects, and maybe even allowing themselves to believe in this year’s marginally retooled club.

There was real momentum, since hope tends to run on solar power in spring training. The plan was going too well. And then Thursday happened, when the Mets announced that ace Kodai Senga likely would be sidelined for Opening Day and perhaps longer due to a shoulder strain.

You could almost hear the brakes screeching.

Senga’s injury now provides the first serious test for the Mets’ blueprint going forward. With a pair of top free-agent pitchers still available — reigning Cy Young winner Blake Snell and World Series champ Jordan Montgomery — can owner Steve Cohen resist the urge to reach for his checkbook?

At the moment, the answer appears to be yes. So says president of baseball operations David Stearns, who was asked Thursday if Senga’s status would increase the chances of the Mets adding someone before the season opener.

“I don’t think so,” Stearns said. “We’re always going to be opportunistic and hear what’s out there, but I don’t think it really changes our thought process.”

Frankly, it shouldn’t. If the Mets truly are committed to getting their finances stabilized for the future, as Stearns has repeatedly suggested, having to wait on Senga’s return can’t be the tipping point. If payroll and the 110% tax rate isn’t a concern, then the Mets should have signed Snell or Montgomery anyway, before losing Senga.

Cohen being a Mets fan with an $18 billion fortune doesn’t mean he’s willing to pay more than double for a player, and that’s what the owner would be on the hook for due to the team’s current tax bracket. For example, signing Snell to a $40 million salary for this season would involve shelling out $84 million total, once you factor in the luxury tab. That’s not smart business, even by baseball standards, and particularly for a club trying to get a better grip on its payroll, something that prompted Cohen to hire Stearns in the first place.

That’s just where the Mets are at this juncture. Both Cohen and Stearns have made no secret of their intentions, either. We’ve witnessed Cohen flex his financial muscles during the first three years after purchasing the franchise, kicking sand in the faces of the other owners. He unabashedly attempted to buy a title, and we applauded him for trying. But that approach ultimately failed, which is why Stearns has now been tasked with devising another path to “sustainable success.”

It’s understandable that the injury to Senga shouldn’t derail that process — if difficult to swallow. We’ve been used to Cohen buying up Cy Young winners like Picassos, so why not another one in Snell? The fact that he’s still paying Max Scherzer and Justin Verlander to pitch for other teams definitely has something to do with Cohen’s policy change, even though he did get back a pair of top prospects — Luisangel Acuna and Drew Gilbert, respectively — by including a big chunk of cash in those trades.

Losing Senga is very damaging to a Mets rotation deep in numbers but perilously thin in top-shelf talent. It means someone like Jose Quintana or Luis Severino could end up on the mound for Opening Day (if they make it through spring training healthy, of course, and there’s no guarantee based on their own medical histories). The Mets will have their fingers crossed these next five weeks.

“We’re going to ask people to step up,” Stearns said. “That’s what happens over the course of a baseball season. We knew we were not going to go through a full season with just five or six starters. And so here we are. We’ve got plenty of options. I’m looking forward to watching that competition in camp. I’m confident that we’ll have guys step up.”

Stearns is a smart guy. Odds are, he’ll figure something out. Maybe some of these dice rolls will pay off. The greatest worry about Thursday, however, was Senga himself. For now, it sounds like he’ll recover fine with simply rest and treatment. Stearns mentioned that Senga has a “posterior capsule strain” — or back of the shoulder — which he characterized as “less bad” than the anterior (front) version. It doesn’t appear that surgery is on the table, so that’s a big sigh of relief for the Mets.

But Senga had arm/shoulder concerns before he came to the States, a factor that led to the Mets getting him at a bargain price of $75 million over five years. They nurtured him through his first major-league season with hyper-vigilant maintenance, and Senga made 29 starts (2.98 ERA) without a blip. After all that, he winds up being shut down less than two weeks into spring training.

This feels like a huge red flag. And now the Mets have to tailor their program for Senga beyond merely his workload. They not only have to get the shoulder right, but protect it going forward. Stearns stated that he wasn’t overly concerned about the injury impacting Senga’s future — “Pitchers are going to get hurt,” he said — and he projected calm regarding the team’s capabilities in the short term.

But the Mets’ strategy for this season got knocked sideways Thursday morning at Clover Park. Now, the greater challenge will be to stay the course.

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