During a radio appearance on 98.5 the Sports Hub on Thursday, Celtics president of basketball operations Danny Ainge said the team is still evaluating Smart's injury and remains uncertain on his opening-night status.
"We don't know enough to determine whether he'll be ready to play opening night or how long he'll be out," Ainge told the Sports Hub. "Obviously, we'll be very careful with him. ... I think over the next few days we'll have a little bit better of an indication on Marcus's ankle and how much it swelled. It didn't seem to be a terrible one but he was in some pain, so it's a little bit concerning."
Smart is expected to undergo further testing Thursday and Ainge said the team would have a better timeline later this week.
Smart rolled the ankle after driving into the lane and stepping on the foot of Knicks guard Justin Holiday. Smart took a couple of hops before lying down on the TD Garden court in visible pain.
Boston opens the regular season at home against the Brooklyn Nets next Wednesday.
It is unknown whether Smart would return for that game.
Smart is entering his third year in Boston. He averaged 9.1 points per game last year coming off the bench for the Celtics.