Celtics' Jae Crowder injures knee thanks to flagrant foul from J.R. Smith

J.R. Smith stays being J.R. Smith, even if he's been quite a valuable piece for the Cleveland Cavaliers since his mid-season acquisition.

Things came close to reaching an ugly boiling point in the series-ending game between the Cavaliers and Boston Celtics on Sunday, with Smith at the forefront.

After Kevin Love's shoulder injury and Kendrick Perkins's flagrant-1 on Jae Crowder, Cleveland's Smith pulled out this hard backhand on Crowder:

Crowder appeared to hyperextend his left knee when he collapsed and had to be helped off the floor. Smith was quickly assessed a flagrant-2 and ejected. It is likely Smith will also be hearing from the league office on Monday.

Crowder meanwhile, was ruled out for the game by the Celtics with a left knee sprain. He'll require an MRI to further evaluate the injury.

It's a disappointing end to the series and season fro Crowder, who hung in admirably guarding LeBron James for long stretches. Until Game 4, the Celtics had been much better with Crowder on the floor than without, with the 6-foot-6 wing doing a nice job staying in front of and bodying up against the four-time MVP.

Crowder averaged 10.8 points, five rebounds and two assists in the series while shooting 51.7 percent from the floor. He averaged 9.5 points and 4.6 rebounds in 24.2 minutes for the Celtics in 57 games after being acquired in the Rajon Rondo trade.

The hope for Crowder will have to be that the injury isn't serious enough to limit his market as a restricted free agent this summer.

Smith, meanwhile, is nothing if not consistent. Two years ago to the day as a New York Knick, he was suspended for an altercation with then-Celtic Jason Terry.