Boston Celtics guard Marcus Smart has been ruled out for up to three weeks with a sprained ankle and a bruised bone.

The 20-year-old sustained the injury in his side's 101-98 win over the Indiana Pacers when he fell awkwardly after clashing with Lavoy Allen.

Smart underwent X-rays at the TD Garden, which proved there was no break, but an MRI scan did reveal that the bone was bruised and his ankle was sprained.

Head coach Brad Stevens told reporters after the game: "We're more worried about the kid than we are about what our lineups or rotations are going to be. We've got a whole 22 hours to figure that out."

The Celtics are 2-3 in their season going into their clash with the Chicago Bulls later today.