Boston Celtics guard Marcus Smart, who vented about the referees on Thursday night, knew he would pay the price for his remarks.

The NBA proved him right Friday, fining Smart $15,000 for his comments. The announcement was made by league executive vice president of basketball operations Kiki VanDeWeghe.

The Celtics earned a 108-87 road victory over the Charlotte Hornets on Thursday, but Smart was not happy after a game in which he was plagued by foul trouble and finished with six points, five assists and two rebounds.

“Really, just, I wish they would call the game the right way,” Smart said postgame. “A lot of calls that they called, I didn’t understand where the fouls were. And it just seems like whenever I get the ball and I’m on offense, I can’t get a call.

“Nobody else is going to protect yourself. You’ve got to protect yourself. So if that means I’ve got to lose a little bit of money, then I’ve got to lose a bit.”

Smart was frustrated in the game, not just by the refs. He also exchanged words with coach Brad Stevens. After Smart was called for a defensive foul and an offensive foul in a span of 11 seconds midway through the third quarter, Stevens subbed Smart out of the game, leading to a minor kerfuffle.

Smart said, “I just was telling him, you know, especially when everything is going that way, like, they’re just picking and picking, and it’s like they’re eyeing on me and it’s like they are doing it on purpose. So I’m telling them like, ‘At some point you have to step in and say something as a coach. But since you won’t, I’ve got to.’

“I understand from Brad’s standpoint, but at the same time, from the player’s standpoint, like, you’ve got to step in.”

Stevens said postgame, “We need Marcus, and I’ve told him a number of times how much we need him. But this is the part about Marcus that I love, right? His fire, his competitiveness. If there’s a moment when he’s upset with us, that’s all part of it. We move on pretty quickly.

“We’ve been together a long time. I’ve been yelled at before and that’s OK. I love him and I trust him. And he’ll get every opportunity.”

Smart, 25, is averaging 9.6 points, 4.7 assists and 3.6 rebounds in seven games (three starts) this season. The 2014 first-round draft pick is in his sixth season out of Oklahoma State.

The Celtics (6-1) carry a six-game winning streak into a Saturday road game against the San Antonio Spurs.