With Marcus Smart’s return this season hanging in the balance, he and the Celtics will now turn to a second opinion for answers.

Smart’s appointment with another local doctor was scheduled for tomorrow, when after a delay because of yesterday’s snowstorm, his team will be fully assembled.

At issue is the initial diagnosis of Dr. Brian McKeon, the Celtics team physician who has told Smart he suffered a torn ligament in his right thumb. The team and player have couched the injury as a sprain, though there is ample fear the tear might be worse than initially thought.

Smart is prepared to play through the injury, though if it is determined he suffered a complete tear instead of a partial one, his season likely is finished, with surgery the primary option. His decision will hinge on whether he can do further damage by playing. The prospect of playing in pain, if the injury is not subject to further damage, is not a problem for Smart.

Recovery from this kind of surgery can take 3-4 months, according to someone familiar with the procedure.

The Celtics thus wait for news of whether their valuable stopper will play again this season. According to a league source, the C’s have no idea about Smart’s probability of return.

“(They’re) waiting for that second opinion,” the source said yesterday. “Don’t know if it’s a 50 percent chance or a 30 percent chance. Just don’t know.”

Smart hit the Garden floor often during Sunday night’s loss to the Indiana Pacers, but one first-half battle for the ball in particular had a foreboding effect in the form of a jammed thumb. After getting his thumb checked by trainer Art Horne, Smart returned to pack 20 points, seven rebounds, eight assists, four steals, six 3-pointers and three drawn charges into 35 minutes — all of it made vital by Kyrie Irving’s failure to return for the second half because of knee trouble.

Smart’s right hand was later put in a cast, and he expressed confidence that “it will be all right. It’s like a sprain right now.”

The degree of sprain, though, could be a problem. As the source pointed out, “a sprained thumb usually means torn ligaments.”

It’s been a tumultuous season for the impending restricted free agent, who was unable to reach agreement on a contract extension with the team last fall. The lack of an extension wasn’t unusual for the Celtics, who rarely extend players off rookie contracts. Though there’s still a good chance Smart will re-sign, he will first have to test the market.

The latest injury also is not the first crisis for Smart’s right hand, which was the object of a 20-stitch gash after he punched a picture frame in a Los Angeles hotel room in January. Smart missed 11 games as a result.

The Celtics hobbled through with a 6-5 record during that stretch, testament to how much they will miss Smart again, and with only 15 games left in the regular season.

Celtics notes

Sunday’s setback was a costly one, considering not just Irving’s departure and Smart’s injury, but a the loss of Daniel Theis for the season. Theis suffered a torn meniscus in his left knee.

Tonight’s game against the Washington Wizards would normally be hyped as a rivalry game on the eve of the playoffs, though to win it, the Celtics will have to do so without Irving, Smart, Theis, Jaylen Brown (concussion) and the player who has been scratched since opening night — Gordon Hayward (leg). All have been listed as inactive.

Al Horford, who missed the Indiana game because of an illness, was listed as questionable.