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NBA Finals Film Study: Celtics One-on-One Defense Slows Down Mavs in Game 1

Kristaps Porzingis dominated for Boston in his return after a 38-day absence in the first game of the NBA Finals.

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BOSTON — Kristaps Porzingis was at his best on Thursday, hitting 8 of 13 shots in his return after a 38-day absence.

But the story of Game 1 of the NBA Finals was on the other end of the court, where the Dallas Mavericks scored just 89 points on 94 possessions. It was the first time in these playoffs that they held themselves to less than a point per possession, and it was their second-worst offensive performance in the 69 total games that Luka Doncic and Kyrie Irving have played together this season.

Doncic scored the game's most points with 30 points, but was below-average in his efficiency (12-of-26 shooting, 2-of-5 free throws). And he recorded just one assist, the lowest of his career in a game in which he played at least 15 minutes (442 total games), although the official scorekeeper may have missed an assist early in the second quarter (see below).

Essentially, the Mavs never really forced the Celtics to change the defensive strategy they had used all season, playing one-on-one or two-on-two and focusing on shooters (especially those in the corners).

Overall, Dallas recorded assists on just nine (25.7%) of its 35 field goals, the lowest rate of any team in any game (regular season, play-in, or playoffs) over the last seven seasons. That's a total of 17,790 instances (8,895 games x 2 teams).

Here are some more numbers and footage of how the Celtics defended Doncic and the Mavs in their 107-89 win.


1. Defend one-on-one

Important number: The Mavs made just 1 of 3 three-pointers from the corner in Game 1, and their only shot came on the game's final basket, a three-pointer from transition in overtime. They averaged 4.6 three-pointers from the corner per game in the first three rounds, a playoff high, but this season they're now 5 of 19 three-pointers from the corner in three games against the Celtics.

On the Mavericks' first possession of the game, the Celtics double-covered Daniel Gafford in the post against Jayson Tatum. But on the second possession not Double Doncic against Jaylen Brown while the other four guys stay home…

Luka Doncic gives in to Jaylen Brown

The Celtics doubled Doncic a couple of times in the post against Payton Pritchard, but for the first 75 seconds of the game, they were more willing to take the ball out of Gafford's hands (in his only post-up of these playoffs) than out of Doncic's hands. And that's probably about the point where they're more likely to see plays.


2. Change and be ready to help

Important number: Doncic had 22 drives in Game 1, the most per game, up from 20.1 per game in the first three rounds. However, according to Second Spectrum Tracking, the Mavs scored just 0.85 points per chance when he made drives, down from 1.12 points per chance before Thursday.

Al Horford was the Boston defender who ran the most pick-and-rolls with Doncic on Thursday, he switched the most of them, and was the defender Doncic took the most shots against.

Horford was beaten twice off the dribble – once by Irving, once by Doncic – during the Mavs' 16-4 third-quarter run that cut a 20-point deficit to eight. But the Mavs' two stars combined to make just 3 of 13 shots against Horford, who even blocked a stepback three-pointer from Doncic.

While the Celtics generally defended Doncic one-on-one and allowed some direct attacks on the basket (forcing him to the right), they often gave him help when he got into the box. Early in the second quarter, he charged Horford, got help from Brown and found Gafford guarding Jrue Holiday under the basket. (Doncic didn't get an assist for that, perhaps because his pass deflected?)

The Celtics also did a great job on Doncic's pump fakes. But late in the second quarter, Derrick White helped with an up-and-under from Doncic on Brown. And he was still able to recover to the corner and force PJ Washington into a swing pass for an above-the-break three-pointer on the break…

Derrick White helps in the color

After the game, White was asked if the Celtics helped, purely within the framework of the game plan or more instinctively.

“It's a little bit of everything,” he said, adding that head coach Joe Mazzulla “gives us the freedom to trust our instincts. And then you also know that when someone gets beat, someone has your back. And after that, we just fly around. So just a little bit of everything and just compete at a high level.”


3. Keep Porzingis out of the action

Important number: While Horford was the one who defended the most Doncic screens overall in Game 1 (15, 18.1 per 36 minutes on the court), it was Porzingis who defended the most per minute (11, 19.3 per 36).

With Horford switching, Porzingis generally played drop coverage against Doncic, staying at the back of the crease to protect the basket. He had a big defensive play early where he helped on a drive and was still able to recover to challenge Derrick Jones Jr. under the basket.

But when Porzingis was higher in his pick-and-roll coverage, Doncic was able to take advantage. He pulled past his former teammate for a difficult basket in the first quarter, and then gave him the Gobert treatment at the end of the first half.

Later in the game, we saw Porzingis try to break up those blocking actions. Midway through the third quarter, when Dereck Lively II made an early block on Tatum, Porzingis told White to switch out and back up to White's man in the corner. White was a little confused, couldn't get a pass to Doncic for the drive, and the Mavs star sank a stepback three.

Early in the fourth, Doncic called for Lively to move up from the baseline to set a block. Porzingis again called for a pre-switch with Pritchard taking the ball after White was blocked. White then followed his instinct (Holiday was behind him, picking up Lively's roll to the basket) and stole the ball from Doncic…

Derrick White steals Luka Doncic

Porzingis, when in the game, will likely be Doncic's main target in the pick-and-roll. We could see even more of that pre-switching in Game 2 on Sunday (8:00 p.m. ET, ABC), and the Mavs will be better prepared.

We can also expect Doncic to be a little more aggressive and forceful in his attacks, taking what Boston gives him while also trying to get more support. And with the Celtics' off-ball defenders more likely to turn to his isolations, other Mavs should make quicker decisions and attack more close-outs to get Boston into the rotation. When Irving gets going, it will obviously be more difficult for the opponent.

The Mavs beat two more of the top five defenses on their way to the Finals and can certainly play better against this team.

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John Schuhmann is a senior statistical analyst at NBA.com. You can email him here, find his archive here and follow him on X.

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