PHOENIX — You think you’ve ingested (or written, in my case) enough spring-training “Best shape of my life” stories to last several lifetimes. That you’d rather see Tony Clark and Rob Manfred exchange nonsensical statements about the dormant free-agent market than listen to one more ballplayer tell you about his life-changing winter.

You need to give these tales of reformation and reinvention another chance.

You must watch Dominic Smith execute a perfect pop-up slide.

“I feel more athletic than I’ve ever been,” Smith told The Post on Tuesday, a few hours after showing off his pop-up slide form. “In spring training, I’ve always looked the part, but as far as my mobility and loosening up some hips and being more flexible, more agile as an athlete, I feel like this is the most advanced I’ve been for sure in my career.”

Holy cow, does he look it. The young man whom a scout once anonymously compared to “Tony Gwynn, when Tony Gwynn was 40 years old” said he’s weighing in at 224 pounds, down about 30 pounds from the end of the 2017 season, and that seems about right. He’s far more compact and limber.

He realizes the error of his past ways, he insisted, and he’s not willing to give up his fight to be the Mets’ Opening Day first baseman, even after his poor big league debut led to the Mets signing veteran Adrian Gonzalez.

Most of all, at a still-ripe 22 years old, Smith yearns to alter his narrative forevermore. He has no interest in being a career-long heavy guy.

“It’s definitely been a fun ride,” he said, “and it’s definitely been a ride I’m ready to just jump off of and never talk about again.”

I’m not an enthusiast for working out alongside ballplayers for the purposes of a story. Most of the time, I feel like, what’s the point?

Last year, in Florida, I watched new Yankee Matt Holliday do everything besides lift a car over his head. Very impressive. And no need to try to match him.

When the offer to work out with Smith arrived, however, I was intrigued. How does a player haunted by physical fitness issues right that wrong? And how well could a schlubby 47-year-old keep up with him?

At about 7:15 Tuesday morning, at the Fischer Institute of Physical Therapy and Performance, strength and conditioning coach Justin Wakefield started warmups for Smith, Brewers catching prospect Jacob Nottingham, a local friend of Nottingham’s named Chris Northrop and me. We began with hurdles (slowly climbing them, without a running start) and did some stretching, shuffling and sprinting drills involving cones.

It was a lower-body day here; there will be another one on Friday. Monday and Thursday are upper-body days and Wednesday is a recovery day.

Smith has been here since early January, staying with his long-time buddy Nottingham (they knew each other in high school and are both represented by Roc Nation Sports), who has been working with Wakefield all offseason. Prior to that, Smith worked at Exos gym in his native Los Angeles. He has reported weekly to Mets strength and conditioning coordinator Dustin Clarke.

“One of his goals, we had to trim down,” Wakefield said of Smith. “We definitely had to trim down. We had to get him moving a little better. Get him a little snappier while strengthening him and making him a little more flexible.”

So we did a lot of aerobic drills. My favorite: a game called “Offense/Defense,” in which you’re matched up against a workout partner in the middle of three cones. The “Offense” person shuffles to a cone on either side, trying to deke the “Defense” person, who must keep up with his counterpart. It was in this game when Smith, working against Nottingham, pulled off his pop-up slide.

“I feel the difference,” Smith said. “I feel like my whole posture is better. The way I walk around is better. My body doesn’t hurt. I just feel more like an athlete. And that’s something that I didn’t have in the past.”

“If you had known him for a long time,” Nottingham said, “you notice a big difference.”

In all, our workout lasted over two hours and incorporated an array of drills, from a “Farmer’s walk” (carrying a significant weight on a bar 20 yards and then returning) to the TRX suspension weight machines to wearing “footies” and using the strength of our arms to slide back and forth on a smooth surface. The emphasis clearly was on mobility and getting your heart rate up, and that made for a far more schlub-friendly experience.

“We’re not moving a ton of weight,” Wakefield said, “but we’re moving weight fast.”

My Garmin device registered more than 800 calories burned. Not bad. Smith and Nottingham headed to a nearby batting cage to get some hitting in, and I went to clean up for our lunch meeting.

Yes, lunch. Exercise is only half of the story, right? Last year, Smith reported to Port St. Lucie, Fla., a relatively svelte 236 pounds, a nice drop from the 254 pounds he carried in 2016. Then, while with Triple-A Las Vegas, he proceeded to gain nearly all of that weight back.

“Just the minor league season, the travel, that was my first year flying, in Triple-A,” he said. “A lot of airport food, lot of night games. Sometimes we’d have early-morning flights and we’d know we were going from the airport to the field. It could be a six- to seven-hour span of not being able to eat.

“You just try to fit in what you can get. It definitely makes it tough sometimes.”

Smith’s downfall historically has not been the sweet, but the savory, he said. Pizza. Burgers. Too often, he ate those after a night game.

Upon getting called up to the Mets last August, he quickly lost six pounds, just by capitalizing on the superior food options in the clubhouse and in the bigger cities. And he vows he won’t fall victim to the same dietary demons that nabbed him in the past.

For lunch, he and Nottingham chose Original ChopShop in Scottsdale, where you can’t break bad. Smith ordered a salad with barbecue chicken and shrimp and drank bottled water. He eats mostly fish, he said, and for about a month this winter, he followed a Pescetarian regimen (a meat-free diet that allows fish). When he isn’t drinking water, he goes with almond-flavored Muscle Milk. When he wants to treat himself every now and then, he goes to Chipotle or eats sushi.

“My uncle, he’s a coach at UNLV,” Smith said. “He showed me things. He teaches his players some things. Carrying the right snacks, carrying the right little things. They teach you all types of protein bars you should eat, the ones you should stay away from. It’s something I’m going to take and pay attention to and make sure, if it is Vegas, I don’t fall into the same thing I fell into last season.”

Will it be Vegas? After Smith underwhelmed with the Mets, posting a .198/.262/.395 slash line with nine homers in 167 at-bats, general manager Sandy Alderson pointedly criticized the first baseman. The Mets signed Gonzalez, traded by the Dodgers and released by the Braves, to a major league contract. Gonzalez has to rank atop the depth chart at first base, though with the Mets paying him just the minimum wage (and the Braves and Dodgers covering the rest), the 35-year-old can easily be released if things change.

“It didn’t bother me much,” Smith said. “I’m pretty excited to have him around. It’s a player that I watched growing up my whole life. … To be able to learn from that and be around that, I’m definitely excited for that and I definitely think it’ll be fun.

“I’m definitely ready to still go out and still battle for a spot. He’s definitely a great player and a great commodity of the league, but I definitely don’t want to fold because of that reason. I want to show the Mets that I am here and I want to be the future first baseman for years to come, and I worked my butt off.”

Mets hitting coach Pat Roessler visited Smith last week, Smith said, and that prompted new manager Mickey Callaway to call him with a salute for the work he has done. Smith said he hasn’t discussed his 2018 assignment vis-à-vis Gonzalez’s arrival with any of his superiors. He doesn’t feel the need.

His rough maiden big league voyage, Smith said, humbled and hardened him.

“My biggest takeaway is that no one will ever feel sorry for you,” he said. “By me learning that, I feel that I matured as a player and I take more ownership. I don’t want to blame anybody for what I did last year. I can’t blame anybody for the weight gain. It was all me. It was the mistakes I made.

“For a second, I kind of felt bad for myself for not playing up to par and being young and being tired, but who cares? The fans don’t care. They want to see me perform. The team doesn’t care. They want to see me perform. So when I really realized that and learned that, I felt like I elevated my game. Now, my confidence is through the roof.”

This week, he’ll wrap up his work with Wakefield and Nottingham, pop back home to LA and then jet to Florida’s Treasure Coast on Sunday, with his first workout at Mets camp tentatively set for Monday.

He’s fluent in social media, yet Smith hasn’t posted much of his new look.

“I want it to be more of a surprise,” he said. “I want them to see me and [have] jaws drop.”

Jaws will drop. Nevertheless, it can’t stop there, Smith knows.

“They just needed to make sure that I came into camp in shape and I’m ready to go. We can check one thing off the list,” he said. “Now it’s time for spring training, and it’s time to get ready and start the battle.”

Best shape of his life. You’ll see it for yourself soon enough.