Boston Celtics big man Kristaps Porzingis has been ruled out for the team’s In-Season Tournament quarterfinal matchup against the Indiana Pacers on Monday, the team announced. Porzingis is currently nursing a calf strain and missed Boston’s previous three games.

Originally, Porzingis left the Celtics’ loss to the OrlanMagic do on Nov. 24 during the third quarter and did not return. After undergoing an MRI in Boston, Porzingis took to Instagram to issue his own update.

“Good news this morning,” Porzingis wrote. “Be back very soon.”

Porzingis noted that he felt a tweak while running and did not slip. That’s noteworthy because the Nov. 24 game was an In-Season Tournament contest, and there have been some concerns about the lack of traction on the new courts that are in use for those games. Earlier this season, Celtics forward Jaylen Brown tweaked his groin after slipping on the Toronto Raptors’ In-Season Tournament court and called the floor “unacceptable.”

In his last appearance, a 17-point loss, Porzingis finished with nine points, four rebounds, two assists and two steals in 22 minutes.

While this issue doesn’t appear to be season-ending, there will be a sense of concern any time Porzingis is on the injury list. He’s only appeared in 60 games once since 2017, and he has suffered multiple major knee injuries in the time since, including a torn ACL and a torn meniscus.

Porzingis has appeared in all but one game this season, but he did deal with plantar fasciitis over the summer, which kept him out of the FIBA World Cup.

Keeping Porzingis healthy is one of the primary objectives for the Celtics, who rely heavily on the big man. He’s one of the few centers who can protect the rim and space the floor at a high level, and he’s been a big part of their early-season success on both sides of the ball. With Porzingis on the floor this season, the Celtics have a plus-10.2 net rating.

Behind him the Celtics have veteran Al Horford, though beyond Horford they have very limited frontcourt depth. Luke Kornet is the only other true center on the team’s roster.