BOSTON -- Celtics coach Brad Stevens says guard Marcus Smart will evaluate his treatment options next week before making a decision about how to progress with an injured right thumb but acknowledged that Smart might not return this season.

Stevens said Smart is waiting to see how his thumb responds to initial treatment while gathering multiple opinions on the injury.

"[Smart will] go talk to another doc about what his chances are of playing without further injury, and also if he needs surgery or not, and what the recovery time would be," Stevens said before Wednesday's game against the Washington Wizards. "After all that information is gathered, he'll make a decision [next week], along with all of us, about the rest of the year."

Earlier in the day, during his weekly appearance on Boston sports radio 98.5 the SportsHub, Stevens admitted that there is the possibility that Smart could be out the rest of the season but said it was too early to know any timeline.

"There could be a slight chance that he's back sooner rather than later, but I'd say that it's not going to be any time too soon," Stevens told the "Zolak & Bertrand" show. "And there's a chance that he would not be back."

In more encouraging news for Boston, Stevens said tests on Kyrie Irving's sore left knee came back clean. He'll miss his second straight game but remains day-to-day while battling the tendinitis that has given him discomfort in recent outings. Irving will travel with the Celtics on their upcoming two-game road trip. Stevens said that while Irving could play in one of the two games, the point guard is "unlikely for Friday." The Celtics play at Orlando on Friday and at New Orleans on Sunday.

"Everything looked great [on Irving's tests]," Stevens said. "Which is good. Just got some soreness and some pain in that knee and, again, not something that you wouldn't have guessed he'd have some of. But obviously, creeping up twice in 10 days, we want to be very careful with that."

Smart suffered what the team has termed a sprained right thumb while diving to the floor during the first half of a loss to the Indiana Pacers on Sunday. Smart had the injury taped and finished with 20 points, 8 assists, 7 rebounds and 4 steals while nearly willing Boston to victory in a game in which Irving sat out the second half because of knee soreness.

Smart downplayed the severity of his injury after Sunday's game, but initial tests Monday showed more worrisome damage to the thumb, forcing Smart to examine his options.

The Celtics were without six players for Wednesday night's 125-124 double-overtime loss to the visiting Wizards, including starters Irving (knee), Al Horford (illness) and Jaylen Brown (concussion). Rookie Daniel Theis tore his meniscus against the Pacers and will undergo season-ending surgery on Thursday. Gordon Hayward is rehabbing from a fractured ankle and is not expected back this season.

Rookie Jayson Tatum woke up with a sore back but was in Boston's starting lineup versus the Wizards and finished with 19 points, 5 rebounds and 6 assists but failed to hit a 3-pointer in the second overtime that would've won the game at the buzzer. Tatum said he thought he simply slept wrong and joked he's getting old after celebrating his 20th birthday last week.

Boston's other starters versus the Wizards: Terry Rozier, Marcus Morris, Aron Baynes and rookie G League call-up Guerschon Yabusele. The team got off to a hot start but squandered a 20-point lead en route to the loss.

Stevens noted that Brown will not travel on Boston's upcoming two-game road trip but is hoping to start the NBA's return-to-action concussion protocol this weekend. If no setbacks, he'll be in line to return next week.

Horford has missed two consecutive games due to illness but is expected back for Friday's game in Orlando.

Asked about all the injuries, Stevens said simply, "next man up." He noted it's a good chance for Boston to evaluate its entire roster as the postseason nears.

"Hey, it's part of it. We have a heck of a challenge in front of us tonight," Stevens said. "More so when you're limited with numbers, but the schedule-maker don't feel sorry for you. The other team doesn't feel sorry for you, so you have to go out and compete."

The Celtics sit comfortably in the No. 2 spot in the East, four games back of the East-leading Toronto Raptors and 6.5 games in front of the surging Pacers.