Celtics big man Kristaps Porzingis said Tuesday that he’s feeling good and making progress in his recovery from the left calf strain he suffered in last Friday’s loss to the Magic and emphasized that he has no big concerns about the injury.

Porzingis left last Friday’s game during the third quarter and missed his second game since suffering the injury on Tuesday against the Bulls. He said an MRI on Saturday revealed that he had a “low-level, low grade strain,” which confirmed his belief that the injury wasn’t serious.

“I knew it wasn’t anything, but just a confirmation that something of course happened,” Porzingis said. “I felt something a little bit. But that it was just gonna be a short recovery. That’s what I was hoping for, and that’s it. …

“This is the NBA, you play every other day and some small things can happen like this. So no big worries, but just looking forward to getting back out there as soon as possible.”

Porzingis suggested that he could get back on a court soon. Celtics coach Joe Mazzulla said that he would be re-evaluated a week from the injury, and Tuesday was the fourth day of his recovery.

“So, already much better and I look forward to keep making fast improvement to get back out there as soon as possible,” Porzingis said.

While Porzingis is encouraged by his progress, the Celtics are still acting in an abundance of caution. Porzingis has never had a calf injury, which can be tricky. He’s almost certain to miss Friday’s home game against the 76ers, but the Celtics’ next game is to be determined based on the results of the In-Season Tournament.

“This is new for me.” Porzingis said. “I guess you have to be a little careful with these kind of things, even though it’s nothing serious, but still, it can be pretty easy I guess to re-aggravate and so the medical staff is being cautious and we’re going to take it slow. But even with taking it slow, it should be a pretty quick recovery.”

Adjustment period

Al Horford has watched and experienced several changes since he was drafted to the NBA in 2007. He’s become an advanced 3-point shooter as the league has evolved in that direction. And, among other things, he’s now noticing a shift into more aggressive offensive rebounding.

Mazzulla has made a clear emphasis in crashing the offensive glass this season to help offset bad shooting nights and create more possessions. It was evident in Sunday’s win over the Hawks, when they pulled down 18 offensive rebounds. It’s not just the Celtics, though. Horford has seen it around the league.

“I think it’s a trend. I think it is trending,” Horford said. “At one point in my career the numbers or whatever were telling everybody to get back – get back on defense, get back on defense. And now I feel like every team is, like, telling people to just go and crash the glass. So it has taken some adjusting from that part because everybody’s usually just kind of hanging out. And not only us, but every team is starting to do that more and more.”

Entering Tuesday, the Celtics’ offensive rebounding numbers were only slightly higher than last season, from 9.7 to 10.3 boards per game, which puts them in the bottom half of the league. Their second-chance points are up from 12.7 per game last season to 14.7 per game this season.

There’s been an adjustment period, especially for the 37-year-old Horford. In Sunday’s win, he grabbed an offensive rebound that had Joe Mazzulla marveling, when he chased down a miss over multiple Hawks defenders. But changing that mindset to hunt offensive rebounds has not necessarily been easy for Horford.

“Because, for me, usually, my whole thing is always just get back on defense, start the transition defense early, get everything back under control,” Horford said. “That’s always been kind of one of the things that I do. That’s why, I don’t know what the numbers say, but I was never crashing on the offensive glass. Now, like, for me to shift that mindset, and it’s like, go to the glass, go get offensive rebounds, get extra possessions. So for me it’s just kind of adjusting for sure.”

One small suggestion

Asked if he’s enjoyed playing in the inaugural In-Season Tournament, Horford described the experience as “different,” and said the league’s goal of making early-season games more relevant has been accomplished. But he did have one suggestion. Horford was not a fan of making last Friday’s game in Orlando – an early afternoon tip the day after Thanksgiving – part of the tournament schedule.

“The schedule was kind of a little messed up, so like I just wish that moving forward, when they do this, they have to make sure that for everybody to be at their best, that somehow the games are being aligned correctly, so it’s not a back to back or it’s not a game that’s kind of like the Orlando situation,” Horford said. “Because I feel like that does matter. It affects the performance and if we want to get the most out of the guys in the In-Season Tournament, you want to make sure they’re at their best.” …

Jrue Holiday, who missed the last two games with a sprained ankle, returned for Tuesday’s game against the Bulls.