Watch: Luka Doncic fouls out amid Mavericks' failed comeback attempt vs. Celtics

Playing with five fouls, Doncic made a bad decision in trying to draw a charge on Jaylen Brown with over four minutes to go in the game. He had 27 points and five assists in the game so far, but he picked up four fouls in the final quarter, some on ill-advised plays.

His first one was an offensive foul on Dallas' first offensive possession, 13 seconds into the final quarter. With 9:24 to go, Doncic got foul No. 4 when he decided to pick up Payton Pritchard full-court. It was an odd decision, culminating in multiple bumps from Doncic that gave the officials no choice but to blow the whistle on him.

Meanwhile, Dallas went on a 20-2 run to shrink Boston's 21-point lead to two points. On his fifth foul, Doncic was arguably hooked by Brown, but Mavericks coach Jason Kidd decided not to challenge the call. Kidd did challenge 26 seconds later, when Doncic was again whistled for a foul on Brown, and the officials held up the original call.

It's a strong answer to anyone who believes the NBA wouldn't let a superstar foul out late in a big game. But mainly it was a demonstration that Doncic simply made bad decisions in the final quarter. The first two of the quarter seemed to happen out of frustration, especially with the Mavericks way behind in the game.

However, it's inexcusable to commit two fouls, and not even shooting fouls, in such a big game. Doncic had four of the first five Dallas fouls in the quarter. While he's never been a defensive star, it was his defensive decision-making that doomed Dallas in Game 3.