Boston Celtics shooting guard Marcus Smart is questionable for Thursday's game against the Sacramento Kings after missing practice today due to illness.

The mercurial Oklahoma State standout has played a vital role for the Celtics in recent years with his toughness and willingness to defend the best two guards in the league.

The Celtics had won three straight games before suffering a 25-point loss at the hands of the LA Clippers on Monday night. They are currently fifth in the Eastern Conference standings, two games back of the Philadelphia 76ers for the third spot in the East.

A potential absence against the Kings would mean Marcus Smart would miss just his second game of the entire season, as he has been a constant rotation player in the midst of a tumultuous year.

Boston was expected by many around the league to be the top team in the East before the season began, but instead, they have been subject to internal criticism from the likes of Kyrie Irving after have struggling to get a foothold among the elite teams in the conference.

Still, Smart has been hailed for his contributions by head coach Brad Stevens, who has been insistent that he should be named to one of the NBA's All-Defensive teams.

Smart is averaging fewer points, rebounds and assists than he did last year, but he has started 47 of 67 games he has played in while posting (by far) the highest Effective Field Goal percentage of his career at over 53 percent.