BOSTON -- On the Dallas Mavericks' fourth possession, superstar guard Luka Doncic tossed a look-ahead pass to P.J. Washington that led to a dunk. It was Doncic's lone assist of Game 1.

Dallas' entire team had only nine assists in the 107-89 loss Thursday to the Boston Celtics.

Not coincidentally, the Mavs had their lowest-scoring outing of this postseason in the NBA Finals opener.

"We've got to move the ball," Mavs coach Jason Kidd said. "The ball just stuck too much. And we'll be better in Game 2."

The Celtics, the league's second-ranked defense this season, succeeded in defending Doncic and his co-star, Kyrie Irving, without double-teaming. Doncic finished with 30 points on 12-of-26 shooting. Irving had an off night while primarily being guarded by six-time All-Defensive selection Jrue Holiday, getting held to 12 points on 6-of-19 shooting with a team-high two assists.

"Just great individual defense," Celtics coach Joe Mazzulla said. "Everybody has to take on the challenge of guarding those guys. They're an amazing team and they put a ton of pressure on you with their ability to score. Everyone is going to take their matchup personal, have personal pride in individual defense."

The alley-oops that the Mavs, especially Doncic, lobbed on a regular basis during their run through the Western Conference playoffs weren't available against Boston. Nor could Doncic create open 3-point looks for his teammates, as he so frequently did while the Mavs defeated three 50-plus-win teams en route to his first Finals appearance.

"They mostly play one-on-one," Doncic said of the Celtics' defensive approach, which employed Jaylen Brown as the primary defender on him. "They don't send a lot of help. So that's why."

Dallas had shot 57% on passes from Doncic during the first three rounds of the playoffs, when he averaged a league-high 8.8 assists per game, according to ESPN Stats & Information tracking. The Mavs went only 1-of-6 from the floor on Doncic feeds in their third Game 1 loss of this postseason.

Doncic's one assist was a career playoff low. So were his six potential assists. He had averaged 15.4 potential assists in these playoffs entering Game 1.

The Mavs' previous low assist total in any game this season, regular season or playoffs, was 14. The nine assists matched the fourth-lowest team total in a Finals game in the shot clock era.

"The ball has got to move a little bit more," said Irving, whose 31.6% shooting from the floor was his lowest in 14 career Finals games. "And again, that starts with me just being able to push the pace, get us some easy opportunities, and just adjust to what they are throwing at us.

"It's a fun series. It was fun going into the game. It's still going to be fun. But there's going to be a level of chess that still has to be played."