Kristaps Porzingis returned from a 10-game layoff to score 20 points off the bench, and the Boston Celtics defeated the Dallas Mavericks 107-89 on Thursday night in Game 1 of the NBA Finals.

Porzingis had not played since Game 4 of Boston’s first-round series against the Miami Heat, owing to a right calf issue. He appeared unaffected by the lengthy layoff, shooting 8-for-13 from the field and grabbing six rebounds and three blocks.

After losing by as many as 29 late in the first half, Dallas rallied in the third quarter, led by Luka Doncic.

The great guard scored 10 points during the Mavericks’ 22-9 run to start the game, and his 3-pointer trimmed Dallas’ deficit to 72-64 with 4:28 remaining.

The Celtics replied decisively, scoring the next 14 points to grab a 22-point advantage.

Daniel Gafford completed the third quarter with a pair of free throws, bringing Dallas within 20, but the Mavericks trailed by at least 17 for the entire fourth.

Game 2 is scheduled for Sunday in Boston.

Jaylen Brown led the Celtics with 22 points, six rebounds, three steals, and three blocks. Jayson Tatum contributed 16 points and 11 rebounds, while Derrick White added 15 points.

Doncic finished with 30 points and 10 rebounds for Dallas, which was outshot 47.6 percent to 41.7 percent overall. P.J. Washington scored 14 points, Jaden Hardy added 13, and Kyrie Irving, who was booed throughout the game, had 12.

Although Porzingis did not get the start, he spent no time establishing the tone after checking in with 7:17 remaining in the first quarter.

The big man tortured his former squad, scoring 11 points and blocking two shots to give the Celtics a 37-20 lead after 12 minutes of play. No team has ever created a greater advantage in the first quarter of a Finals game.

Boston kept piling it on, going on a 14-2 run to lead 58-29 with 4:11 left in the second quarter. However, Doncic erupted for nine points in the final four minutes of the first half, bringing the Mavericks within 63-42 at the intermission.