Smart was injured in Sunday's loss to the Magic, along with forward Jayson Tatum.
The Celtics initially announced Smart would be out for the game, calling it a "hip contusion", but ESPN's Adrian Wojnarowski reported it was something a bit more serious (and concerning, for Boston) as a strained oblique. Boston, however, came up short missing a few three-point attempts under 2:00 left in the game that would have either given the Celtics a lead or brought them within a point of tying the game. This win secured Orlando their first trip to the playoffs since 2012, so it's definitely safe to say that the Steve Clifford-coached Magic were playing with a much greater intensity than Boston. Tatum has a left shin contusion.
Smart fell to the ground after colliding with Magic center Nikola Vucevic midway through the third quarter.
Stevens will nearly certainly rest both during Tuesday's regular-season finale at Washington.
The two players left Sunday's game early and did not return and were not available for the media after the game.
The Celtics announced Monday that at least seven players will not suit up for Tuesday night's matchup against the Washington Wizards. Although he said that the five-year veteran looked sore, he was trying to walk while he was in the locker room. I don't know, for whatever reason when he - when he jumped in the first quarter he felt it. However, he's expected to be good to go for the start of the playoffs. The Celtics don't sound too concerned with Tatum's injury (Stevens wasn't even aware of it before the game), but they also weren't going to take any chances with their second-leading scorer this season.