Late in the fourth quarter of the Celtics' 107-94 victory over the Cavs last night, JR Smith took a cheap shot at Al Horford while he was in the air looking to throw down a lob from Marcus Smart. After the All-Star center was sent careening to the floor, Smart quickly got in the face of Smith in defense of his teammate.

JR was ultimately assessed a flagrant foul 1 following a review by the officials, and received a pleasant "Fuck You JR" chant from the TD Garden crowd. Check out the footage below.

Smart defended his reaction during the post-game press conference, telling reporters that it wasn't the first time that JR has "done some dirty stuff, especially against us."

"Oh, man, we're out there to play basketball," Smart said. "You know, and I just looked at it: Al is a defenseless person. He's in the air. He can't control how his body goes, and he's not even looking. And you go and take two hands to the back; that's a dirty shot. You just can't allow that to keep happening."

"That's not the first time JR has done some dirty stuff, especially playing against us," Smart added. "He's known for it, especially playing against us. We know that. So, you know, it's like a bully: You keep letting a bully keep picking on you, he's going to pick on you until you finally stand up, and that's what I tried to do. One of my guys was down, and I took offense to it."

Even JR couldn't argue that the officials made the right call giving him a flagrant for shoving an airborne player.

"It was a good call," Smith said after the game, in which he finished with zero points on 0-for-7 shooting. "I blatantly pushed him. It wasn't like I was trying to low-bridge him or something to make sure he didn't get it. It was a good, hard foul. I can understand why they gave me a flagrant."

Horford, who scored eight points in a 90-second span to ice the game, told reporters, "I felt like it was uncalled for, that type of play there, but that's the one thing about the group of our guys. We have each other's backs, and it is what it is. We moved on to the next play, and we just locked in even more after that."