PORT ST. LUCIE, Fla. -- The work began immediately. Shortly after arriving at Clover Park on Saturday and changing into Mets gear for the first time, J.D. Martinez grabbed some lumber and stepped into one of the right-handed batter’s boxes across from the bullpen mounds. For about 10 minutes, he tracked live pitching from new teammate Adrian Houser. Martinez went from there to an indoor cage, then to the stadium itself, where he took a few hacks on the main field.

All parties involved have a vested interest in the ability of Martinez, who sat out nearly all of Spring Training before signing a one-year, $12 million deal with the Mets this week, to ramp up as quickly as possible. But there’s no great rush. Because Martinez has already consented to starting the season in the Minor Leagues, he will by rule have to spend at least 10 days there. The earliest Martinez can debut is April 7, nine games into the season.

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That gives him time to prepare at his relative leisure.

“It’s kind of weird,” Martinez said. “You can train as hard as you want all offseason, but nothing gets you ready for baseball like actual baseball.”

Martinez added that he hasn’t seen a 100 mph fastball since last October, when his Dodgers lost in the National League Division Series to the Diamondbacks. Since that time, he had been hitting four to five days per week at Nova Southeastern University, his alma mater in Florida, while waiting for an acceptable offer. Last month, the Giants came calling, but Martinez was wary of the sizable outfield dimensions at Oracle Park. At 36 years old, Martinez is cognizant that even a middling season could effectively end his career.

“If I go there and I hit .260 with 20 [home runs],” Martinez said, “people are going to say that I’m old and I’m washed up and I’m kind of done, and [I’ll] find myself out of the game. I wanted to give myself the best opportunity.”

In New York, Martinez will have every chance to be the same type of hitter he was last year, bashing 33 home runs with an .893 OPS. He’s going to start at DH nearly every day. Manager Carlos Mendoza plans to bat him cleanup, creating protection for Pete Alonso. Perhaps unsurprisingly, Alonso was vocal in his advocacy for the Mets to sign Martinez, urging team officials as well as their mutual agent, Scott Boras, to complete a deal.

“I’ve watched this guy play for quite a bit now on the other side of the dugout,” Mendoza said. “But for us to have him now on my side is special. He’s going to be an impactful hitter, obviously. The lineup is deeper.”

Since news of Martinez’s signing first broke, Mets types have also been effusive about what Martinez can add off the field. His knowledge of hitting, they say, is unparalleled. His clubhouse presence is noteworthy.

Upon arriving at the batting cage Saturday morning, Martinez threw an arm around the shoulder of teammate Mark Vientos, with whom he’s worked for years during the offseason at Bommarito Performance Systems in Davie, Fla. No one stands to lose more playing time in the wake of Martinez’s signing than Vientos, who had been set to become the Mets’ regular DH. On his first day in camp, Martinez addressed that proverbial elephant in the room, telling Vientos that talent, always, will find its way to the big leagues. He used the slow start to his own career as a prime example.

Martinez laughed as he recalled those early days, which resulted in the Astros -- with David Stearns as an assistant general manager -- releasing him at the end of Spring Training 2014. When Martinez reunited with Stearns this weekend, he quipped: “Last time you came in this office with me, it didn’t end well.”

“That was a long time ago,” Stearns replied. “Big mistake.”

Now, Martinez is the furthest thing from unwanted. He says he’s “addicted to the playoffs,” and the Mets are relying on him to take them there. So excited was Mendoza to add Martinez that the manager offered him uniform No. 28, his long-time number, free of charge. (Mendoza, who never actually wore 28 in a regular-season game, switched to 64.)

“He said, ‘What do I need to do to get No. 28?’” Mendoza recalled of the conversation. “I said, ‘Hit a lot of homers.’ … I’m happy to give it up.”