BOSTON — Al Horford continues to be a key contributor for the reigning NBA champion Boston Celtics despite being one of the oldest players in the league. The veteran is in his 18th season in the NBA at 38 years old as his teammates view him with reverence in the locker room.

But the game has changed significantly in Horford’s near-two decades in the league, and that includes the big man himself. It’s why Horford credited a key improvement to his game — 3-point shooting — that has allowed him to extend his career.

“For me, physically, it has added years to my career, I feel like,” Horford said. “It’s been good for me, and I think Brook (Lopez) saw it as well, and it’s been a great benefit. And that’s what I was mentioning, that now, like the guys are coming in from college, and they’re already shooting it, and they’re confident, they’re giving them the green light, and it’s a good thing.”

Horford attempted a total of 65 3-pointers in his first eight seasons in the league, all in Atlanta, spanning 496 games. In comparison, he’s attempted 101 3s this season in just 19 games. Horford started to put up more 3s in his final season with the Hawks, when he attempted 256 of them in 2015-16. Including that season, Horford has put up 2,311 3-pointers in 601 games since then. So, that’s a huge jump compared to when he came into the league.

In present day, the 3-pointer is not just a key part of Horford’s game but a huge part of the league. The Celtics lead the NBA by a wide margin in 3-point attempts as the majority of their shots come from behind the arc. Horford is just one of numerous willing shooters on the roster.

But Horford’s career arc is interesting in the sense that he was able to adapt to the modern game. The league wasn’t so 3-point heavy when he came in, but with the rise of the Warriors and Stephen Curry last decade, the analytics have changed. Celtics Coach Joe Mazzulla has leaned into the math mindset, which is why his team is also more than willing to put up those shots. Horford’s development as a shooter started all the way back in Atlanta, crediting the decision-makers back then.

“Specifically, it was Rick Sund, was the GM of the Hawks at the time, so he’s the one that first pushed me for it,” Horford said. “And then as far as coaches go, there was two, and it was (current Cavs coach) Kenny Atkinson and (current Suns coach) Mike Budenholzer. So Coach Bud as the head coach, he just gave me the freedom and the confidence, but Kenny Atkinson was the one that was working with me continuously and giving me confidence as well during that process.”

KRISTAPS PORZINGIS hurt his right heel in the win over the Wizards on Sunday, but it continues to sound like the injury isn’t serious. Porzingis left in the first half and didn’t return because of what the team called right heel pain.

Porzingis said after the Wizards game he wasn’t worried about his heel and that he came out for precautionary measures. Celtics coach Joe Mazzulla shed some more positive light Wednesday. A day earlier, Mazzulla mentioned Porzingis’ injury is day-to-day.

“He got through practice well, looked pretty good,” Mazzulla said. “We’ll see how he is (Thursday), see how he responds to it. But I thought he looked good today.”

The Celtics are in a break of their schedule as they had three days off between Sunday’s win in Washington D.C. and Thursday’s game against the Bulls at TD Garden.

But for now, everything sounds relatively positive. Porzingis being able to go through practice is a good sign that he should be ready Thursday. If he isn’t able to play, the Celtics will just rely on their cast of depth big men like they have to start the season.

Porzingis missed the opening month of the season while in surgery rehab, as he needed to get his rare left foot injury from the NBA Finals fixed over the summer. But he came back ahead of schedule. He’s been injury prone throughout his career, so it’s no surprise the team was cautious with his right heel pain from the Wizards game. The Celtics need him available in the playoffs, after all, instead of pushing him in the regular season.

“I banged up my heel a little bit,” Porzingis told reporters in Washington. “I kept on playing. It was nothing major, honestly. More like a precautionary thing. It was pretty sensitive. I told the medical staff and they just pulled me out of the game. I don’t think it’s anything major.”