NBA Finals Film Study: Celtics' one-on-one defense slows Mavs in Game 1
In Game 1 of the NBA Finals, the Celtics became the 1st team to hold the Mavericks under 90 points this postseason.
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BOSTON — Kristaps Porzingis was feeling it on Thursday, shooting 8-for-13 in his return from a 38-day absence.
But the story of Game 1 of the NBA Finals was the other end of the floor, where the Dallas Mavericks scored just 89 points on 94 possessions. It was the first time they’ve been held under a point per possession in these playoffs, and it was their second least efficient offensive performance in 69 total games in which Luka Doncic and Kyrie Irving have played together this season.
Doncic scored a game-high 30 points but on below-average efficiency (12-for-26 shooting, 2-for-5 from the line). And he registered just a single assist, tied for the lowest total of his career in any game in which he played at least 15 minutes (442 total games), though the official scorer might have missed an assist early in the second quarter (see below).
Essentially, the Mavs never really forced the Celtics to adjust how they’ve defended all season, playing one-on-one or two-on-two and staying at home on shooters (especially those in the corners).
In total, Dallas recorded assists on just nine (25.7%) of their 35 field goals, the lowest rate for any team in any game (regular season, Play-In or playoffs) in the last seven seasons. That’s 17,790 total instances (8,895 games x 2 teams).
Here are some more numbers and some film on how the Celtics defended Doncic and the Mavs in their 107-89 victory.
1. Defending one-on-one
Number to know: The Mavs were just 1-for-3 on corner 3-pointers in Game 1, and the only make was the last basket of the game, a transition 3 in garbage time. They averaged a playoff-high 4.6 corner 3’s per game through the first three rounds, but are now 5-for-19 on corner 3s in three games against the Celtics this season.
On the Mavericks’ first possession of the game, the Celtics double-teamed Daniel Gafford in the post against Jayson Tatum. But on the second possession, they didn’t double Doncic against Jaylen Brown, with the other four guys staying at home …
The Celtics doubled Doncic in the post against Payton Pritchard on a couple of occasions, but in the first 75 seconds of the game, they were more willing to get the ball out of Gafford’s hands (on his one, and only, post-up of these playoffs) than Doncic’s hands. And that’s probably about who they’re more willing to see make plays.
2. Switch and be ready to help
Number to know: Doncic had a game-high 22 drives in Game 1, up from 20.1 per game through the first three rounds. But, according to Second Spectrum tracking, the Mavs scored just 0.85 points per chance when he drove, down from 1.12 points per chance prior to Thursday.
Al Horford was the Boston defender who was put in the most pick-and-rolls with Doncic on Thursday. He switched most of those and was the defender against whom Doncic took the most shots.
Horford got beat off the dribble twice — once by Irving, once by Doncic — on the Mavs’ 16-4, third-quarter run that cut a 20-point deficit down to eight. But the Mavs’ two stars combined to shoot just 3-for-13 against Horford, who even blocked a Doncic stepback 3.
While the Celtics generally defended Doncic one-on-one, and allowed a couple of straight-line drives to the basket (forcing him right), they did often bring help when he got into the paint. Early in the second quarter, he drove against Horford, drew help from Brown, and found Gafford sealing Jrue Holiday under the basket. (Doncic wasn’t awarded an assist on that one, maybe because his pass was deflected?)
The Celtics also did a great job of staying down on Doncic’s pump fakes. But late in the second quarter, Derrick White helped on a Doncic up-and-under against Brown. And he was still able to recover out to the corner, forcing a swing pass for an above-the-break 3 from P.J. Washington …
After the game, White was asked about when the Celtics were helping, if it was strictly about the game plan or more instinctual.
“It’s a little bit of everything,” he said, adding that head coach Joe Mazzulla “kind of gives us the freedom to trust our instincts. And then you also know that, like, if someone gets beat, someone’s going to have your back. And we just fly around after that. So just a little bit of everything and just competing at a high level.”
3. Keeping Porzingis out of the action
Number to know: While Horford was the guy defending the most total Doncic ball-screens (15, 18.1 per 36 minutes on the floor) in Game 1, it was Porzingis defending the most on a per-minute basis (11, 19.3 per 36).
While Horford was switching, Porzingis was generally playing drop coverage against Doncic, staying back in the paint to protect the rim. He had a big defensive play early where he helped on a drive and was still able to recover back to contest Derrick Jones Jr. under the basket.
But if Porzingis was higher in his pick-and-roll coverage, Doncic was able to take advantage. He drove past his former teammate for a tough bucket in the first quarter and gave him the Gobert treatment at the end of the first half.
Later in the game, we saw Porzingis ask out of those screening actions. Midway through the third quarter, when Dereck Lively II was setting an early screen on Tatum, Porzingis called for White to make the switch, retreating to White’s man in the corner. White was a little scrambled, wasn’t able to play Doncic to drive, and the Mavs star drained a stepback 3.
Early in the fourth, Doncic called for Lively to come up from the baseline to set a screen. Porzingis again called for a pre-switch with Pritchard, who took the ball after White was screened. White then followed his instincts (Holiday had his back, taking Lively’s roll to the rim) and stole the ball from Doncic …
Porzingis, when he’s in the game, will likely be Doncic’s primary target in the pick-and-roll. We could see some more of that pre-switching in Game 2 on Sunday (8 p.m. ET, ABC), and the Mavs will be better prepared for it.
We can also expect Doncic to be a little more aggressive and forceful with his drives, taking what Boston gives him while also trying to draw more help. And with the Celtics’ off-ball defenders shading toward his isolations, other Mavs should be quicker with their decisions and attacking more close-outs to get Boston in rotation. If Irving gets going, things obviously get tougher for the opponent.
The Mavs beat two other top-five defenses on the way to the Finals and they can certainly play better against this one.
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John Schuhmann is a senior stats analyst for NBA.com. You can e-mail him here, find his archive here and follow him on X.
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