ATLANTA — Marcus Smart is unsure if he’ll play in Sunday’s Game 4 after the Celtics guard suffered a lower back injury from a hard fall late in Friday’s Game 3 loss to the Hawks.

With 2:33 remaining in the fourth quarter on Friday, Smart jumped up to grab a defensive rebound but fell straight on his tailbone. He stayed down on the court for several moments before getting up and walking gingerly. Smart stayed in the game, but he was still experiencing some soreness on Saturday.

“I’m OK,” Smart said. “I’m a little sore, obviously. Rewatching the play, I took a hard fall. I didn’t realize how high I was. But I’m OK, relatively speaking. Little sore today. See how I feel tomorrow, though. Not really sure where we’re at right now with playing but we’ll see.”

Smart said before the postseason began that he felt as healthy as he’s been at this stage of this season in years, but this injury is one that he’s had before. He said there’s not much he can do as far as treatment other than letting it heal on its own. There’s still some discomfort when he walks around.

“A little bit. Nothing crazy,” Smart said. “But it’s a reoccurring injury as well. So a little scar tissue built up. But for the most part, I’m OK. It’s better than I expected to be at this moment, so that’s a good sign.”