After gliding through preseason streaking and healthy, the Celtics were unable to escape training camp Wednesday without adversity.

While the team watched its five-game winning streak snapped in a 121-96 loss against the Knicks at TD Garden in the preseason finale, the Celtics also lost swingman Marcus Smart to a badly sprained left ankle sustained in the second quarter.

Celtics coach Brad Stevens said Smart would be re-evaluated Thursday “but the early indication, he’s had an ankle sprain or two in the past, it looks like it’s not too long term. We don’t what it means. We’ll have a better idea the next couple of days.’’

Smart rolled his ankle landing on the right foot of New York’s Justin Holiday after dishing a pass to the wing. Smart collapsed in pain under the basket and was carried off the court to alleviate placing any pressure on his left leg.

It has been an otherwise healthy preseason for the Celtics, who only dealt with Gerald Green’s sprained hip flexor in the first week of camp. If Smart misses any extended time, players such as Terry Rozier, Jonas Jerebko, and rookie Jaylen Brown will have to soak up his minutes.

Stevens gave four of his starters — Isaiah Thomas, Avery Bradley, Jae Crowder and Al Horford — the night off and Amir Johnson played just nine minutes. Rozier got the start and continued his impressive preseason with 13 points — shooting 3 for 4 on 3-pointers — in 14 minutes and Brown led the Celtics with 17 points on 5-for-14 shooting.

With Carmelo Anthony getting the night off, the Knicks relied on second-year big man Kristaps Porzingis and he looked season-ready with 20 points in 22 minutes. Kyle O’Quinn added 13 points off the bench.

The Celtics will have six days off before their season opener against the Brooklyn Nets at TD Garden. Boston begins the season with three games in four nights, and they may be without Smart.

“We practice every day, that could happen in practice,’’ Stevens said of Smart’s injury. “That was just a unique thing, as he’s driving down the court he just stepped on someone’s foot. He twisted it and that’s why we ultimately have a team so that we can make up for a loss of a key contributor, if necessary.’’

Bentil to Maine?

The Celtics had eight picks in June’s draft, which is good for them but not necessarily great for some of the draftees who were trying to find a spot on a crowded roster.

Boston ultimately traded two of the picks and used two more on European players who have been stashed overseas, but the team did make four other picks, including former Providence standout Ben Bentil at 51st overall.

The forward signed a three-year contract that is partially guaranteed this season, but he will almost certainly be waived before Monday’s roster deadline and join the Celtics’ D-League affiliate, the Maine Red Claws. Bentil’s $250,000 guarantee is unusually high for a draft pick in this situation, but it is a kind of token of appreciation and a carrot that would make him more amenable to joining the Red Claws as an affiliate player.

Entering Wednesday’s preseason finale against the Knicks, Bentil had appeared in two exhibition games for the Celtics, averaging 3.5 points and 3.5 rebounds in 12 minutes per contest.

“Camp went pretty good,’’ Bentil said on Wednesday, as he sat on the bench after completing a rigorous pregame workout. “I learned a lot and bonded with my teammates and learned a lot about this next level and just grew as a person, grew as a team player.’’

Bentil, who had 8 points and six rebounds in the Celtics’ 121-96 loss to the Knicks at TD Garden, said that over the past month he has improved his ability to read the game, make small but important plays, and turn down good shots in favor of great ones. If he goes to Maine, the Celtics would lose their rights to him and any NBA team would be able to sign him.

“It’s another platform for other people to see you and see what you’ve got,’’ he said. “Every night you’ve got to come ready to play and showcase what you’ve got.’’

Still, Bentil said his preference would be to remain in the Celtics’ organization.

He said he is eager to rejoin other teammates from training camp like Damion Lee, Marcus Georges-Hunt, and Jalen Jones, and he knows that other young Celtics will probably shuttle between Boston and Portland during the regular season.

“That’ll be awesome,’’ he said. “We grew so much together in camp, so it’d be an experience and a blessing to play with them and continue to grow the chemistry. I just want to be an ultimate good player all around, a player that my coaches and teammates can count on, so that’s basically what I’m going out there to develop.’’

Roster decision due

There is still little clarity regarding the Celtics’ plan for their final roster spot. Boston has 16 players under fully guaranteed deals and needs to whittle that number to 15 by Monday at 5 p.m. Many roster decisions around the league will be made by Saturday evening, though, giving released players time to clear waivers and sign elsewhere before rosters are finalized.

The Celtics continue to explore potential trades that could make it unnecessary to cut a player, but the return in such a deal would likely be light.

If the situation remains unchanged, the belief is that the battle for the final roster spot will be between R.J. Hunter and James Young.

The Celtics coaches and executives have maintained that it is one of the more difficult choices they have had to make, and Stevens reiterated that point on Wednesday.

“These guys have all gotten better, and it’s a tribute and testament to them,’’ Stevens said, “because it’s not only not easy to get better and to keep a good mind-set about you and be confident, but they’re probably dealing with a lot of stress. And to continue to improve, continue to come with a smile and work every day and do those types of things is a testament to these guys, and we’re going to have to make hard decisions.’’