ESPN analyst rips Mavericks star Luka Dončić's 'unacceptable' attitude in NBA Finals: 'He is costing his team'

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The Boston Celtics took a commanding 3-0 lead in the NBA Finals on Wednesday night. No team has ever come back from that deficit in NBA history.

The Dallas Mavericks have an outside shot at making history. To accomplish it, their biggest star will need to put himself in check, ESPN's Brian Windhorst says.

Mavs superstar Luka Dončić is averaging 29.7 points, nine rebounds and nine assists in the series' first three games, so his on-court performance is hardly the issue.

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Dallas Mavericks guard Luka Dončić looks for a foul call during Game 3 of the NBA Finals against the Boston Celtics at American Airlines Center in Dallas on Wednesday. (Barry Chin/The Boston Globe via Getty Images)

However, Windhorst took exception to a "terrible play" Dončić made when he told his bench, "You better bleeping challenge" a call that gave him his sixth foul of the night, "as if it was the bench's fault."

That was the beginning of an all-time rant from Windhorst, who criticized Dončić's attitude.

"I’m standing here in the Mavericks’ tunnel. Over there is the Celtics’ tunnel. That’s where the winners are," Windhorst quipped. "If Luka’s ever gonna be a winner coming out of this tunnel here, he is gonna have to use what’s happened in this finals as a learning experience.

"You’ve got a situation here where Luka’s complaining about the officiating. They have begged him, they have talked with him [and] they have pleaded with him. He is costing his team because of how he treats the officials."

Luka Dončić of the Dallas Mavericks reacts during Game 3 of the NBA Finals against the Boston Celtics at American