Kristaps Porzingis is available for the Boston Celtics in Friday night's Game 4 of the NBA Finals, but will "only be used in specific instances, if necessary," head coach Joe Mazzulla said.

Porzingis had been listed as questionable before going through an on-court workout about 2 1/2 hours before tipoff. He sat out the Celtics' Game 3 victory over the Dallas Mavericks because of a lower left leg injury he suffered in the third quarter of Game 2.

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."

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.

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.

Al Horford has started all three Finals games for the Celtics, including the two when Porzingis played.