Boston Celtics guard Marcus Smart says NBA players are "gonna end up protecting ourselves eventually" in altercations with fans after he got tangled up with a spectator during Friday's game against the Denver Nuggets.

In the fourth quarter, Smart fell into the front row of the crowd at the Pepsi Center while chasing a loose ball. When he got up, he exchanged words with a fan nearby.

"My foot got stuck in a chair, and the fan told me, 'That's right, stay on the ground, get on your knees,'" Smart said after the Celtics' 96-92 loss. "Excuse me? You know what I'm saying. I just told him, 'Listen, just watch the game.'"

NBA spokesman Tim Frank said Saturday that the league is investigating the matter.

Smart said he was not satisfied with the security response after he pointed out the fan.

"I told them who it was. They just looked at him and didn't even say anything to him," Smart said. "... Probably if I was a superstar, they probably would've did something for it. It is what it is.

"We're gonna end up protecting ourselves eventually, and it's not gonna be pretty for those fans. We don't want that, the league doesn't want that, we don't want that as players, but at some point you have to stand up and you gotta protect yourself as a man."

Video showed staff members talking to fans in the area of the incident, but no action was taken.

The Nuggets told The Denver Post that security looked into the incident but could not determine what happened.

In college at Oklahoma State, Smart was suspended for three games in February 2014 when he shoved a Texas Tech fan. Smart had told Cowboys coaches the fan had directed a racial slur at him, ESPN reported at the time.

Smart said he will look to move on from his latest incident but noted that player/fan altercations are an ongoing issue.

"That's a problem in the league that we gotta fix, because if we retaliate to protect ourselves, we're the ones getting in trouble -- they're not -- and that's not right," he said.