PHILADELPHIA – Paul Pierce is reminiscing about his first playoff game in 2002, a best-of-five series against Allen Iverson and the Philadelphia 76ers.

Pierce dropped 31 points on the Sixers on 25 shots in a Game 1 victory for the Boston Celtics.

“Remember when I used to take 25 shots?” he said with a hearty laugh.

That is no longer his role. Pierce is 37 years old, averages a career-low 26.4 minutes a night for the Washington Wizards and provides seasoned wisdom to the electric backcourt of John Wall and Bradley Beal.

“I tell them, ‘Learn from all the stuff I did (wrong) when I was young,”’ Pierce said.

Before that 2002 playoff game against the Sixers, Pierce didn’t pore over film or engage in any carefully selected stretching routines. Instead, he wandered over to Burger King and ordered a Whopper and a large Coke.

“I can’t remember last time I had a soda,” Pierce said. “It tastes like acid to me now.”

In a sitdown with, Pierce mused about the changes he’s made to improve his longevity, his disastrous season in Brooklyn, his championship year in Boston and the playoff chances of a young Wizards team that he believes “has all the tools to get to the Eastern Conference finals.”

Pierce reports he is 225 pounds, the first time in his career that he’s been under 230 for a playoff run.

He eschews fast food, follows a strict weight training regimen during the season, drinks mostly water (“and an occasional red wine,” he adds wryly) and stretches for nearly an hour before every game. Despite his reduced role (his 12.2 points and 4.0 rebounds a game are also a career low), Pierce said he loves playing basketball for Washington.

Despite a star-studded lineup, the Nets failed to live up to expectations, losing in the second round. Jim McIsaac/Getty Images

“I’m much happier,” he said. “It was a tough situation (in Brooklyn) last year. Horrible, really.

“It was just the guys’ attitudes there. It wasn’t like we were surrounded by a bunch of young guys. They were vets who didn’t want to play and didn’t want to practice. I was looking around saying, ‘What’s this?’ Kevin (Garnett) and I had to pick them up every day in practice.

“If me and Kevin weren’t there, that team would have folded up. That team would have packed it in. We kept them going each and every day.”

The player that puzzled him the most, said Pierce, was point guard Deron Williams.

“Before I got there, I looked at Deron as an MVP candidate,” Pierce said. “But I felt once we got there, that’s not what he wanted to be. He just didn’t want that.

“I think a lot of the pressure got to him sometimes. This was his first time in the national spotlight. The media in Utah is not the same as the media in New York, so that can wear on some people. I think it really affected him.”

Pierce said veteran Joe Johnson was an affable professional but also a reluctant leader.

“Joe is quiet,” Pierce noted. “He doesn’t want much attention. He doesn’t say much.

“There’s a lot of secondary guys on that team. KG and I went there looking at them as the main guys who would push us, because we were advancing in years. But we ended up doing all the pushing.”

Brooklyn gave up its 2014 pick (which the Celtics used to draft James Young) and unprotected picks in 2016 and 2018 to acquire Pierce, Garnett and Jason Terry. They believed they were poised to be championship contenders, but posted an underwhelming 44-38 record and were bounced by the Miami Heat in the second round of the playoffs.

When the season ended, they declined to sign Pierce to a new deal and let him walk as a free agent.

Before I got there, I looked at Deron as an MVP candidate. But I felt once we got there, that’s not what he wanted to be. He just didn’t want that. I think a lot of the pressure got to him sometimes. The media in Utah is not the same as the media in New York.”

Paul Pierce

“I would have stayed in Brooklyn because of Kevin,” Pierce said. “I told him, ‘I don’t really like this situation but I would never leave you if you want me to stay.’ But they decided not to re-sign me so I never had to make a choice. I would never have left Kevin like that.”

Garnett was traded in February to Minnesota, where he will eventually assume a front-office role as a part-owner.

“He’s happy,” Pierce said. “I’m glad he waived his no-trade clause. I told him, ‘They don’t appreciate you in Brooklyn, man.’ They didn’t even use him right.

“He’s where he’s supposed to be. He IS Minnesota. He never sold his house there.”

Pierce said he still talks to Garnett every week and credits him for introducing him to the benefits of a hyperbaric chamber, which Pierce sleeps in for 2-3 hours before every home game to boost recovery and healing.

Garnett introduced him to the treatment in 2009 shortly after they won an NBA championship together. Pierce said he has found lying in the chamber, which enables him to breath oxygen in an atmospheric pressure raised up to three times more than normal, has helped him improve his circulation, reduce inflammation, increase his stamina and expedite the healing process.

According to the website Carolina Hyperbarics, oxygen normally is transported through the body only by red blood cells. But the hyperbaric chamber, according to the website, converts the oxygen to “a solution that is carried in all of the body’s fluids, including plasma, central nervous system, lymph and bone.”

Pierce is so sold on the chamber’s benefits he’s been encouraging Wall to try it and has urged the Wizards medical staff to purchase one for the team. Although he doesn’t travel with the chamber during the regular season, he plans to pack up the foldable bed and the two metal engines and transport them with him during the playoffs.

“It’s great for recovery,” Pierce said. “It’s definitely helped me. It’s the size of a little coffin. You just get in it, zip it up and you’re good.

“The first time I tried it felt like I was suffocating, like there was no air. But now I’m so used to it I’m asleep in a matter of minutes.”

Today’s players will enjoy longer careers, Pierce believes, because teams are so tuned into nutrition, conditioning and body maintenance. He said his talks with the younger guys mostly center on social media and “the things I did before Twitter and Instagram.”

Boston’s Big Three: Kevin Garnett, Paul Pierce and Ray Allen. Fernando Medina/NBAE/Getty Images

“I talk to them a lot about mental preparation and consistency,” Pierce said. “I keep telling Wall and Beal, ‘You’ve got to make up your mind. Do you want to be good, or do you want to be great? Because if you want to be great, you gotta do it every single night, not just when you feel like it.’

“Both of those guys have the potential to be great. I love them. But sometimes I’m not sure they realize what it takes.

“That was (Rajon) Rondo’s problem, too. Some days he did, some days he didn’t. I think it’s more this generation. A lot of these players have been catered to since the sixth grade. The NBA is changing so much. It’s not like when I came up, with that old-school mentality that practice really mattered. You’ve got these 24, 25 year old guys who sit out of practice now to rest. It’s hard for me to understand, but I’m trying.”

Pierce was sidelined for three games with an injured toe, but the true cause, he said, was to rest a sprained right knee he has been slogging through for a month. In his previous six games before he finally took a seat, Pierce was shooting just 25.6 percent from the field and averaging single digits.

The Wizards plugged in former No. 3 pick Otto Porter Jr. in Pierce’s place and he responded by averaging 13.6 points and nearly seven rebounds a game over past four outings.

“Otto is another one who just doesn’t understand how good he is,” Pierce said. “He can shoot, he’s a slasher, he can defend, I’m just not sure how badly he wants it every day.

“That kid just needs to get mad. If he came to practice ticked off and to the games ticked off, he’d be fine. But it’s hard to get Otto mad. I should punch him one day just to get him riled up.”

The Wizards will likely draw a first-round series with either Chicago, whom they split games with this season, or Toronto, which has won all three games they’ve played.

“We haven’t done particularly well against Toronto, but I don’t feel they have the ‘It’ that makes you worried,” Pierce said. “There isn’t a team I look at in the Eastern Conference that makes me say, ‘They are intimidating, we don’t have a chance.’

“As good as Atlanta is, they just don’t give off that aura where we’re afraid of them.

“You definitely have to worry about Cleveland because they have LeBron and some vets now, but if we get to the conference finals, anything can happen.”

It was a weird relationship. We were all good friends on the court, but Ray always did his own thing. That’s just the way Ray was. Even when we were playing together, we’d be having a team dinner and Ray wouldn’t show up. We’d go to his charity events but Ray wouldn’t show up to somebody else’s.”

Paul Pierce

Some of his young teammates can recount his battles with LeBron, both in Miami and Cleveland, nearly verbatim. They bring up Christmas Day performances that Pierce had long forgotten. The camaraderie, he said, is refreshing.

Pierce still engages in group texts with former Celtics teammates (and coach) Doc Rivers, Garnett, Kendrick Perkins and Big Baby Davis, but hasn’t talked to Ray Allen since he bolted from Boston to Miami in the summer of 2012.

Though much has been made of it, Pierce said, people don’t understand he wasn’t all that close to Allen to begin with.

“It was a weird relationship,” Pierce conceded. “We were all good friends on the court, but Ray always did his own thing. That’s just the way Ray was. Even when we were playing together, we’d be having a team dinner and Ray wouldn’t show up. We’d go to his charity events but Ray wouldn’t show up to somebody else’s.

“I called him on it. I said, ‘Man, Ray, we support all your stuff but when we ask you, you don’t come to ours.’ I remember when Rondo re-signed with Boston, we had a little dinner at a restaurant and Ray didn’t show up.

“I know Ray probably didn’t like Rondo that much, but it wasn’t a fact of not liking somebody. You don’t have to like everybody you play with — it’s a matter of showing support.

“Rondo probably didn’t like Ray either, but he came to Ray’s functions to show, ‘Hey, we’re together in this.’

“It’s not a bad thing with Ray. We had a great relationship on the court. But even the year we won it, after a game we’d say, ‘Let’s go have something to eat and have a night with the older guys.’ We’d get there and it would be me, Kevin and Sam (Cassell), but no Ray. In a lot of ways, me, Sam and Kevin were our Big Three.

“It just got to the point where it was, ‘That’s Ray.’ No hard feelings. Everyone made such a big deal of us not talking after we left, but there really wasn’t much there.”

Pierce was riding the bus with Kevin Seraphin last Tuesday when Seraphin informed him he was 9 years old when Pierce was drafted.

Like most veterans, Pierce has his fair share of regrets. He wishes he paid closer attention to his body in his younger years, and wishes he was paired with KG sooner “so we could have made a longer run together.” He wishes he was younger when his rivalry with LeBron James commenced.

Pierce is firm: Next season will be his last.

“I’ve had my time,” he said.

That doesn’t mean one of the NBA’s most prolific trash talkers is done stirring the pot.

“I always say I wish I was in my prime matching up against LeBron,” said Pierce, grinning. “Let’s see how many championships he would have won then.”