Celtics' Smart leaves game vs. Knicks with Achilles strain

The Boston Celtics suddenly are a little thin in the backcourt, at least for the moment. Rookie point guard Marcus Smart left Friday's game against the New York Knicks with an apparent left Achilles strain and was ruled out for the rest of the game.

The Celtics were already without Avery Bradley Friday, who sat out with flu-like symptoms. 

Smart, the No. 6 pick in the 2014 NBA Draft, has had a difficult rookie season so far, missing 11 games previously with an ankle injury. He's averaging 6.6 points per game.