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Boston Celtics guard Marcus Smart wasn't happy after picking up five fouls in his team's 108-87 victory over the Charlotte Hornets on Thursday.

After the game, Smart told reporters he was frustrated with what he believed was a lack of protection from the officiating crew in terms of calling fouls on Hornets players.

"I wish they would call the game the right way," he said, per NBC Sports Boston's Chris Forsberg. "... If nobody else is going to protect yourself, you’ve got to protect yourself. So if that means I gotta lose a little bit of money, then I gotta lose a little bit of money."

Smart's fifth foul came in the third quarter, and he appeared to gesture toward his team's bench as he walked off the floor.

Complaints about referees are nothing new. In a poll conducted by The Athletic in April, 17 of the 58 players interviewed identified officiating as the NBA's biggest issue. It was the biggest share (29.3 percent)  of the overall results.

"The emphasis the refs have to put on certain calls throughout the game, I feel like that's the biggest challenge, especially for physical players," one player anonymously responded, per The Athletic's Sam Amick. 

Smart would probably agree with that comment because he isn't afraid to get physical with opponents, who will respond in kind.

The NBA now allows head coaches one challenge over the course of a game. Beyond the fact a coach can only use it once, regardless of whether the challenge is successful, the decision about whether to review the call has to be made so quickly it's difficult to determine whether it's a worthwhile pursuit.

In short, a coach's challenge has the potential to correct a bad call but doesn't necessarily address the root of the problem.

Smart alluded to the fine he's likely to receive for his comments, and he's probably not going to be the last player to vent his grievances with the performance of the referees.