Marcus Smart is an important part of the Boston Celtics' hopes to bring the NBA championship back to TD Garden, but now the Celtics aren't sure if they will get him back at all this year.

Mark Murphy of the Boston Herald reports:

League source says Celtics don't know probability of Marcus Smart playing again this season. “(They're) waiting for that second opinion. Don't know if it's a 50 percent chance or a 30 percent chance. Just don't know.”

According to Adrian Wojnarowski of ESPN Smart has a tendon injury in his right thumb and the Celtics are still trying to figure out what the best plan of action is next.

He injured his thumb during Sunday's game against the Indiana Pacers when he dove on the ground for a loose ball. He was able to finish the game but was in obvious pain during the postgame interview.

He tried to downplay it as something that wasn't a big deal and that wouldn't affect his play. “Sore, but it will be all right,” said Smart. “It's like a sprain right now.”

But it is clearly more than just a sprain and it might end up costing the Celtics guard a chance to finish the season. Smart has played in 52 games this year and is averaging 10.2 points, 4.8 assists and 3.5 rebound per game.

His importance to the team though can't all be measured on the stat sheet. He is a really good defender and is always giving 110 percent on both sides of the ball.

Without him, someone else is going to have to step up and be the glue guy for the Celtics.