The Celtics' game plans throughout the Finals have been one of the big reasons why they have built up a 3-0 series lead. They've made it a point to attack Luka Doncic and, to a lesser extent, Kyrie Irving. Those two have not held up particularly well in 1-on-1 matchups or in help responsibilities.
Joe Mazzulla put maximum pressure on both of those two in the second half of Game 3 by using the same play over and over to involve them. The Celtics scored in five different ways off the play, exposing Luka and Kyrie's defense. It was a great halftime adjustment to take advantage of the way the Mavs were guarding, which turned the tide of the game.
The play: The Celtics empty corner pick-and-roll with Jayson Tatum and Jaylen Brown
Empty corner pick-and-rolls are a common action in the NBA. The name is exactly as it suggests — it's a pick-and-roll with no offensive player occupying the corner.
The Celtics ran this play to start the second half with Tatum setting a screen in the pick-and-roll. Knowing that the Mavs were going to switch on the screen, they got Tatum a mismatch on Irving.
White fed it to Brown, who had the angle to get Tatum an easy layup.
The Celtics ran that same play four subsequent times, using Tatum and Brown in those empty corner actions in order to force Irving and Doncic into defending them. Each time, they found a different weak point in Dallas' offense.
Why it matters
Doncic was roundly criticized for his poor defense in Game 3. ESPN analyst Brian Windhorst went off on him, calling his defensive effort "unacceptable. He's a hole on the court."
Windhorst is right, but there's some context needed as well. The Celtics came in with a beautiful halftime adjustment in order to put maximum pressure on Doncic. He was forced into guarding a ton of actions, tiring him out and contributing to him fouling out with over four minutes left in the game.
Mazzulla has earned criticism ever since taking over the team last year. He has found clever ways to attack Doncic and Irving that the Wolves couldn't do in the previous round. He deserves a ton of credit for the ways in which he has gotten his two best offensive players on the two weakest links for the Mavs.
That empty corner pick-and-roll was the adjustment of the Finals. It may have earned the Celtics their 18th banner.