Mets catcher Francisco Alvarez during a spring training workout on Feb....

Mets catcher Francisco Alvarez during a spring training workout on Feb. 28 at Clover Field in Port St. Lucie, Fla. Credit: Newsday/Alejandra Villa Loarca

PORT ST. LUCIE, Fla. — Francisco Alvarez doesn’t keep the tool that got him to the majors — his bat — in his locker at Clover Park.

He does keep the tool that might help keep him there — his catcher’s mitt — right in the front of the locker.

“I’ve had this one for three years,” Alvarez said, in English while wearing the well-worn glove.

If Alvarez can turn that mitt into something major league pitchers like to aim at, he could turn out to be what the Mets are dreaming of — a power-hitting, All-Star-level catcher.

For now, at age 21, Alvarez is a phenom at the plate (despite a slow spring training) and a work-in-progress behind it.

The Mets signed catcher Omar Narvaez to a one-year free-agent deal with a player option for 2024 just before Christmas and inked Tomas Nido to a two-year extension about a month later.

So that gives Alvarez time to develop his catching skills — something that pitcher Carlos Carrasco recently volunteered that he is doing quite well.

Carrasco threw a minor-league rehab game to the then-teenaged Alvarez in 2021.

“That’s the glove I used when I caught Carrasco,” Alvarez said, beaming with youthful exuberance.

Alvarez pointed out that he also used it when he caught Max Scherzer in a rehab game in Hartford, Connecticut, last summer, after which Scherzer praised Alvarez’s work behind the plate.

Carrasco has been throwing again to the 5-10, 233-pound Alvarez in spring training and has enjoyed the experience.

“Really good,” Carrasco said. “It’s a big target back there. He’s really good calling the pitches, all that kind of stuff. He’s getting way, way better. I had the opportunity to throw to him in 2021, and from then to now, he’s been doing really good. A big difference from 2021 to now.”

Last Sunday, Carrasco allowed three runs to Tampa Bay on two long home runs. But he was helped when Alvarez whipped a throw to first base to pick off a runner in the third inning.

“Impressive,” Buck Showalter said. “I almost missed it. I started to look away.”

Of course, the tool that you don’t want to miss is Alvarez’s bat. If you look away when he’s at the plate, you might miss a 432-foot, 108.9-mph home run, which is what he hit on Oct. 4 for his first big-league hitafter starting 0-for-8. Or you might miss the 107.8-mph double in his next at-bat.

Those are both of Alvarez’s hits in the first 12 plate appearances of his career. After going 0-for-2 with a walk while in the lineup to catch Carrasco again on Friday night, Alvarez was 3-for-23 in spring training.

Alvarez thought he had his first home run when he hit a drive to left in the third inning, but Marlins leftfielder Bryan De La Cruz scaled the fence to bring it back.

If he had a chance to make the Mets’ Opening Day roster, that chance likely is gone, given his struggles at the plate. Barring an injury, Narvaez and Nido will be the Mets’ catching tandem come Opening Day.

Alvarez eventually could figure into the designated hitter spot, which for now is a platoon of fan favorite Daniel Vogelbach from the left side and much-less-than fan-favorite Darin Ruf from the right.

The Mets are confident that Alvarez’s bat will play in the majors as long as he gets consistent at-bats. In the minors in 2022, Alvarez hit 27 home runs with an .885 OPS in 495 plate appearances.

But the club’s roster is not set up for Alvarez to get consistent major-league at-bats. Hence, the focus in spring training has been on Alvarez’s defensive growth.

“I feel like I’ve grown tremendously in these last two years compared to 2021 when I first caught [Carrasco],” Alvarez, who felt more comfortable switching to Spanish for a formal interview, said through an interpreter. “You get the repetitions, you get that game experience, so the more you do that, it’s going to be leaps and bounds in comparison.”

And about making the Mets’ Opening Day roster, Alvarez said: “Honestly, since the end of last season, that’s been the goal the entire time.  If it happens, great, and if it doesn’t, that’s fine as well. I’ve still got to keep working.”

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