MIAMI -- Boston Celtics center Kristaps Porzingis hobbled off the court before halftime of Monday night's 102-88 Game 4 win over the Miami Heat and did not return with what the team said was a right calf injury.

Porzingis will undergo imaging Tuesday, but early indications are that he didn't sustain an Achilles tendon injury, sources told ESPN's Adrian Wojnarowski.

Porzingis appeared to tweak something after catching a pass from Jaylen Brown late in the second period. Upon getting the ball, Porzingis started driving toward his left, then grimaced before quickly giving the ball back to Brown and coming up lame in the middle of the play. Porzingis didn't appear to be touched by anyone on the play during which he was hurt.

As he walked to the locker room with a support staffer, Porzingis briefly held his jersey over his face in apparent frustration.

The Celtics quickly released an update, saying Porzingis was suffering from right calf tightness and was doubtful to return to action.

Veteran big man Al Horford took his place in the starting lineup to begin the second half.

Celtics coach Joe Mazzulla said he had not gotten a postgame update on Porzingis' condition.

"I didn't see what happened," Mazzulla said.

The 7-foot-3 Porzingis, who joined the Celtics last offseason via trade with the Washington Wizards, fit his new team almost perfectly, averaging 20 points and seven rebounds per contest while giving Boston an even more dangerous five-out offense.

The Celtics lead the best-of-seven series versus Miami 3-1.

The Associated Press contributed to this story.