Kristaps Porzingis is officially listed as questionable for Game 4 of the NBA Finals, and the Boston Celtics aren't offering much insight into the status of their big man for Friday's game.

Porzingis, whose rare lower left leg injury kept him out of Game 3 against the Dallas Mavericks, didn't do an encore with reporters two days after he answered questions about his injury.

Celtics coach Joe Mazzulla didn't offer much insight, either, which means Thursday's injury report will be the closest thing to any official word on whether Porzingis' latest ailment will keep him out of Game 4 on Friday night (TV: 8:30 p.m. ET, ABC).

Boston moved within a victory of an 18th championship without Porzingis, beating Dallas 106-99 on Wednesday for a 3-0 series lead. The Celtics are poised to break a tie with the Los Angeles Lakers for the most NBA titles.

The 7-foot-2 Latvian has a dislocated tendon in his left leg, caused by a tear of the tissue that holds tendons in place. The team has called the injury rare, and Mazzulla labeled it "serious."

Porzingis played the first two games of the NBA Finals, with a crucial role in the Game 1 win, after missing the previous 10 playoff games with a strained right calf.

"Kristaps has gotten better from yesterday to today," Mazzulla said Thursday. "He's fighting like hell to play. But it's going to be up to us to protect him and to make sure that it's in the best interest for him as a player and as a person."

The injury happened in the third quarter of Game 2, when Porzingis said he knocked knees with Dallas rookie center Dereck Lively II when they went for a rebound on a free throw.

Al Horford has started all three Finals games for the Celtics, including the two when Porzingis played, and Xavier Tillman Sr. had a 3-pointer during a 20-5 Boston run while playing for the first time in the title series with Porzingis out.

"We've been playing all season and all playoffs without him," star guard Jaylen Brown said of Porzingis. "Obviously, we'd love to have him out there. We are different when he is. But X stepped in that role, and I thought he was great."

Porzingis signed a $60 million, two-year extension with the Celtics after they acquired him in a trade with Washington last summer. That deal kicks in next season.

The Associated Press contributed to this report