Kristaps Porzingis sat out Game 3 of the NBA Finals, then dressed but did not play in Game 4.

His status for Game 5 on Monday night remains to be seen, but one of the big man’s backups offered a less-than-promising update ahead of Sunday’s Celtics practice.

“I mean, we’ll see,” Xavier Tillman said when asked whether Porzingis will be healthy enough to see the floor as the Finals shifts back to TD Garden. “Obviously, like (the team) said, it’s a rare leg injury, so obviously if he’s going through excruciating pain where he can’t be his best, it might not be worth it. …

“When we go through our practice, he’s doing some stuff, but you can still tell that he’s very uncomfortable. So we don’t want to put him in any type of situation that could really, really hurt him.”

Porzingis was the last player to take the court Sunday. He practiced his close and midrange shooting under the watchful eye of a Celtics trainer and appeared in good spirits, laughing and joking with teammates.

The 7-foot-2 center remained largely stationary during the portion of practice that was open to the media, however, and sported bulky braces on both ankles. He did not speak with reporters.

The Celtics have been without Porzingis for most of this postseason. He missed 10 consecutive games with a calf injury suffered during the opening round, returned for Games 1 and 2 of the NBA Finals, then sat out both games in Dallas with what Boston called a “rare” ankle injury.

Porzingis was excellent off the bench in the first two games against the Mavericks, presenting matchup problems on both ends of the floor. The Celtics won Game 3 without him to take a 3-0 series lead, but they were routed in Game 4, losing 122-84 as the Mavs staved off a sweep.

“We miss him a lot,” guard Jrue Holiday said. “(He’s a) top-three player on our team. Scoring, defense at the rim, blocking shots, comedic relief. It’s been great playing with him, and we wish that he was out here with us.”

Al Horford has started every game for Boston since Porzingis’ initial injury, and the latter’s latest absence opened a spot in the rotation for Tillman, who logged 11 impactful minutes in Game 3 after playing sparingly during the Celtics’ run to the Finals.

“I’ve done a lot of watching from him and Al and figuring out, like, OK, that’s the role of the fives when they step on the court as far as spacing, as far as defensively and stuff like that,” said Tillman, whom Boston acquired from Memphis at the trade deadline. “And (Porzingis) has also done a good job of just giving me tidbits to look for, whether it’s offensively or defensively.”

Tillman played just seven minutes in Friday night’s loss, all in the first half, with head coach Joe Mazzulla opting to give reserve bigs Luke Kornet, Oshae Brissett and Neemias Queta extended runs in garbage time.

Kyrie’s regret

Mavericks guard Kyrie Irving has faced frequent questions about his ill-fated Celtics tenure during these Finals. One such prompt on Sunday yielded an illuminating response.

Irving said he regretted the way he handled his trade to the Celtics in 2017, saying he should have done more to embrace the franchise’s rich history and connect with Boston’s stable of NBA champions.

“When I look back, getting traded here, it wasn’t one of my (top) options,” he said. “It wasn’t like No. 1 on my list. So when the trade opportunity got approached to me, instead of going back and appreciating the Celtics’ history, I just came in with an open mind and just kind of like, all right, I’m just going to go with the flow into this. But I think that was the wrong approach. Just being young.

“Now being older with hindsight looking back, I definitely would have taken time to know the people in the community and talked to some of the champions that have come before me and actually extend myself to them instead of the other way around, expecting them to be there giving me advice. Because they have been through this. They have championship pedigree here. They have shown it for years. They are one of the most winningest franchises in all of sports.

“So you have to show your respect here. I think that’s what I struggled with initially, figuring out how I’m going to be a great player here while winning championships and also leading a team and selflessly joining the Celtics’ organization or the cult that they have here. That’s what they expect you to do as a player. They expect you to seamlessly buy into the Celtics’ pride, buy into everything Celtics.

“And if you don’t, then you’ll be outed. I’m one of the people that’s on the outs (laughs). I’m perfectly fine with that, you know what I mean. I did it to myself. They don’t welcome me with a warm embrace, even though I know a lot of people in the organization and I’m friends still with some of them. But, yeah, doing it to myself. And that’s what I was talking about in terms of accepting the choices.

“But looking back, I would have shown my respect and have more of a council around me from some of the Boston Celtics that came before me to explain what the pressure is like.”

The Mavs’ Game 4 win snapped Irving’s personal 13-game losing streak against Boston. He finished with 21 points, six assists and four rebounds to help Dallas avoid elimination.