Joe Mazzulla orders Celtics players to intentionally foul Bulls center Andre Drummond while winning in-season tournament game by 32 points... as he tells Chicago coach Billy Donovan they need to keep 23-point lead to advance

The Boston Celtics employed a controversial tactic to advance to the knockout round of the NBA in-season tournament on Tuesday night.

While leading the Chicago Bulls by 32 points at TD Garden, Celtics coach Joe Mazzulla instructed his players to continuously foul opposition center Andre Drummond in an attempt to suffocate the closing stages of the game.

By doing so, Mazzulla felt his team would boost their chances of keeping their point differential high enough to advance to the quarterfinals of the in-season tournament.

Head-to-head matchups were used as tiebreakers to advance to the next round when two teams in the same group finished with the same record. But for three teams, both point differential and total points came into play.

Boston therefore chose to send Drummond to the line for six free-throw attempts in the game, with the Chicago star making just one of them.

After noticing what was going on, Bulls head coach Billy Donovan looked visibly unhappy at the side of the court before conversing with opposite number Mazzulla.

The latter then appeared to explain his team's situation in the tournament, with Boston needing to win by at least 23 points to have a chance of making it into the quarterfinals.

Donovan then appeared to acknowledge that he understood before walking away and watching the remainder of the game.

The ploy worked for Mazzulla, however, as his team won a three-team tiebreaker with the Brooklyn Nets and Orlando Magic and will be the No 3 seed in the Eastern Conference, with No 2 seed the Indiana Pacers up next.

Yet his rough and crafty tactics did not go down well with Donovan, and Bulls insider KC Johnson claims he apologized for them in the hallway after the game.

Donovan then told reporters after the game: 'Andre is a veteran guy and I told Mazzulla, "What are we doing here?"

'I get keeping your guys in, wanting to get in [to the next round]. The league's made it a big deal. 

'But [the Celtics] also, in fairness to them, they gotta deal with the rules too. If they're trying to get into Vegas [where the semifinals and final will be played], there's things they gotta do. 

'For me, it was just the fouling. And Joe was great when I talked to him. He understood.

The Celtics made a season-high 21 3-pointers, getting four each from Al Horford and Jrue Holiday. All five Boston starters scored in double figures. 

'To be honest, it was a little weird but the ultimate goal was to come out and get a win tonight and that's what we did,' Celtics star Jaylen Brown said, noting that that focus on point differential was more than a little unusual. 

'It´s tough because that's just not how the game is supposed to be played. One, you've got to respect your opponents.'