PORT ST. LUCIE, Fla. — The road back from the left shoulder injury has been long and tedious with even some outbursts of anger, but David Wright is swinging a bat again pain free and insists he is right where he needs to be for 2015, a season in which he expects to be playing in October.

Yes, an October playoff run. Again. Finally.

“I feel really good,’’ a sweat-soaked Wright told The Post this past week after a grueling 2½-hour workout at the Mets’ new Barwis Methods indoor training facility located under the right-field stands at Tradition Field. “I’m 100 percent confident that I will be physically ready to go.’’

Make no mistake, for all the young pitching and Matt Harvey’s golden return, Wright will have to deliver a big year for the Mets to reach the playoffs for the first time in nine seasons. His injured left shoulder, classified as a rotator cuff contusion by the team, must remain stable and Wright must produce.

“For me, personally, last year sucked,’’ Wright said. “When you have a passion for something and you fail at it, I want to make sure that never happens again. If I do what I’m capable of doing, we’re a different lineup.

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“I fully expect us to be in the playoffs,’’ the 32-year-old Wright said of the upcoming season. He was 23 the last time the Mets were in the postseason. “It’s not coming out here and boasting, but I think where we stand right now, we’re a much better team than we were last year and in years past. You win with young, dominant pitching and we have quite a bit of that, and offensively, we are going to be better than we have been.’’

Where exactly is Wright in his comeback from a season that saw him hit a career-low eight home runs and post a career-low .698 OPS over 586 plate appearances?

“I’m hitting off a tee, doing flips [tosses],’’ Wright said. “It’s still pretty controlled, which is fairly normal for this time of year. I feel good. Now it’s just a matter of me trying to get my left shoulder on a par with my right shoulder, just strength-wise. I feel pain free, which is good, feel like the shoulder is healthy, and now it is just a matter of building up that strength.

“In my eyes, I’m not too far behind from where I am normally at this time of year.

“But it was such a slow and tedious process because rehabbing your shoulder is so boring,’’ Wright said of the two-month program he went through here under the supervision of Mets physical therapist John Zajac. “These guys were so good with me because there was some days I came in real ornery and started yelling at them and stuff.’’

That is a much different side of David Wright, but pain and frustration can take a toll.

Watching him swing again and do a series of shoulder exercises — this wasn’t just any workout — is the kind of news Mets fans have been waiting for since last season.

Wright and many other Mets have embarked on this new offseason training program with Mike Barwis of the Discovery Channel show “American Muscle.”

“This is going to give me a big advantage,’’ Wright said. “So many of the guys are here, we come in, do our workouts, go over to the field and do our baseball stuff and usually have dinner together.

“You’re pushing each other. I don’t think too many teams are doing this.’’

Here is the ultimate testimonial for the Barwis system:

“I’ve always worked out in the offseason, but I wish I would have had something like this earlier in my career,’’ Wright said.

“It’s not just about getting yourself the strongest and the fastest. Everything we do in here is engineered, and it will translate to the baseball field.

“We’re all paying to do this. To see the dedication of all the guys throughout the organization is pretty impressive.’’

On this day, Lucas Duda, Jon Niese, Bobby Parnell, Travis d’Arnaud, Jeurys Familia and Rafael Montero, among others (including the Indians’ Michael Brantley), went through the session with music from the likes of Naughty By Nature. In all, 30 players from the Mets organization (even Ruben Tejada is back) are participating in the six-week program. The Mets have named Barwis to supervise their strength and conditioning program on every level from rookie ball to the majors. The facility is open to the public as well.

Duda is the poster child for its success, having participated last offseason in Michigan and exploding with a breakout season, hitting 30 home runs, third-best in the National League. He is thrilled to have Wright working alongside him.

“David sets the example,’’ said Duda, who also has October expectations. “He’s our guy. If he maintains his health through 162, I think we’ve got a pretty good shot. There is no doubt in my mind he is going to return to the guy he is.’’

The goal, said general manager Sandy Alderson, who stopped by to observe the workouts, is for players to “reach their full potentiality.’’

Mets chief operating officer Jeff Wilpon told The Post he is “very excited for the season and this just adds to it. We have another six weeks before the team reports, and these guys are already down here working.

“Mike is doing this for the entire organization,’’ Wilpon said of Barwis, a consultant with the Mets since 2011. Barwis first met Wilpon when he was strength and conditioning coach at Michigan.

“All our minor league trainers are here, too. Mike has trained a tremendous amount of athletes through the years. You can see the enthusiasm that’s here. They believe in this program. It’s very satisfying to see the buy-in because I didn’t push this. This is about improving performance.’’

Wilpon knows the Mets’ strength is pitching, the depth of the pitching.

“I know everybody wanted Sandy to do this or do that to get something, but keeping your strength is important as well,’’ Wilpon said. “And with these guys here, somebody out of this group is going to step up like Duda did last year.’’

Wilpon pointed out the program helped others last year as well, such as Wilmer Flores, Juan Lagares and prospect Matt Reynolds.

Barwis has 24 years of experience. He is a geyser of enthusiasm.

“We are completely holistic and run through every body part that you can possibly fathom,’’ he said in his loud, raspy voice. “But the other things we do that most people don’t really understand are balance and functional stuff that teaches them to control their body in three-dimensional space, explosive training, transferring power from the upper to lower extremity effectively, flexibility, injury prevention, making sure we stabilize the joints that are commonly injured in the game.’’

All that bioenergetic conditioning is about one thing, said Barwis, who has trained more than 500 Olympic and professional athletes in 40 sports.

“Let’s make him a better baseball player,’’ he said. “More efficient, more refined, explosive. Our goal is to impact people’s lives. It’s about giving the New York Mets what they need from a bunch of guys who want to win championships. The fans want to win the championships, obviously the coaches want to win the championships, the players really, really want to win the championships. That’s the thing that is overlooked, and they are willing to come in here and grind this hard. They want to win.’’

As Duda blasted 30 home runs last year, Barwis said, “Every time he hit it out of the park, I ran around the house like a little kid.’’

And, according to Barwis, Wright’s shoulder “looks fantastic.”

“The goal is to create stability about the joints, alleviate imbalances while improving performance,” he said. “David Wright is a guy who comes in with the mentality every day that I’m going to bring energy, lead this army and make this happen. Those kind of guys are easy to coach.’’

There are more changes with the Mets. Wright is excited to be working with new hitting coach Kevin Long and assistant Pat Roessler, both former Yankees. He began working with Roessler this past week, calling the experience “awesome.”

“We should have one of the more dominant starting fives or sixes or sevens in baseball,’’ Wright said. “Offensively, with [Michael] Cuddyer, that obviously helps, and I expect a lot more out of me this season. I think [Curtis Granderson] would say the same thing. Continued progress from Lagares, Flores, d’Arnaud, so there are a lot of things to be optimistic about offensively, but ultimately we are going to win with our pitching.’’

Wright’s message to the long-suffering fans is simple.

“The thing that solves all problems is winning,’’ he said. “The burden is on us as players and as an organization to go out there and win baseball games.

“If we start winning baseball games in April, the fans will come out, but we have to prove we have a good product on the field.’’

Wright added, “I’m preparing my body for a long season.”

A season that includes an October playoff run.

“Yes,’’ Wright said. “It’s very important that from Day 1 these expectations and these goals, no matter what the expectations are from the outside, the expectations from the inside are that we are preparing to be a playoff team.

“That is where the bar is set. The bar is not set to be just better than last year [79-83] or to be a .500 team. The bar is set to be a playoff team.’’

Time to muscle up, Mets.