Sullinger said he felt some discomfort in the foot the day after Boston closed the first half of the season with a win over the Atlanta Hawks on Feb. 11. Sullinger removed himself from Boston's practice when the team reconvened in Sacramento on Wednesday and team trainer Ed Lacerte took him for tests Thursday that revealed the injury to the fourth metatarsal.
"Jared is going to be out a while," Celtics coach Brad Stevens said. "Supposedly it happened in the Atlanta game and he was talking a little bit about it [Wednesday], with regard to feeling some discomfort and so he went through a little bit of practice, then pulled himself out. Ed took him to get the X-ray [Thursday], so that's not good news on the Jared front, that's for sure."
Added Stevens: "He's not going to play on this trip, and I don't anticipate him playing any time soon."
Sullinger wore a protective walking boot over his left foot as he watched practice. He was emphatic that he wouldn't need surgery, but admitted there's no immediate timetable for his return.
"They didn't tell me a lot, they just told me I'd be out a little bit," Sullinger said. "It sucks, honestly. Especially with the type of [playoff] push we're trying to make. For me to not be a part of it on the court -- I'm trying to help the team from different angles."
Sullinger said after the team's practice Thursday that he would stay with the Celtics for the duration of a three-game road trip, but they announced Thursday night that Sullinger would return to Boston for further testing.
The Celtics were hoping to get second-year big man Kelly Olynyk back shortly after the All-Star break, and he was on the practice court Thursday at Sleep Train Arena engaging in some light shooting. But Olynyk is not healthy enough to engage in contact work and will not play Friday against the Kings.
Olynyk has missed 11 straight games due to a sprained right ankle.
"I'm playing it by ear," he said. "See how it feels every day."
Added Stevens: "Kelly did a little bit more [Thursday], but nothing that would indicate that he would play [Friday]. We're going to be small, real small [Friday]. We'll have to figure that out."
The Celtics worked Thursday with Tyler Zeller on the first unit playing alongside Brandon Bass. Boston has had success with smaller lineups and will have to lean on those groups while Olynyk and Sullinger work their way back, or until reinforcements arrive.
Shavlik Randolph, acquired last month from Phoenix, has not appeared in a game for Boston while battling a hamstring ailment. But he practiced the past two days and should be available against the Kings.
Boston will need him. The Celtics are expected to be extremely shorthanded due to injuries and sending out two players -- Marcus Thornton and Tayshaun Prince -- at the trade deadline. Boston could get additional frontcourt help once 6-foot-10 forward Jonas Jerebko, acquired from Detroit, joins the team and gets up to speed.
Asked about playing without Sullinger, Avery Bradley said: "It takes away a really good player that helps us out on both ends of the floor. It's hard to replace him. But you have a lot of guys that have high confidence that are very good players and someone's going to get a chance to go out there and help our team however they can."
Sullinger was confident his teammates would step up in his absence.
"The type of team we have and the type of attitudes we have as a team, especially with the guys that are here, they understand what we need to do, how we need to play, and the grit and the grind that we need to win basketball games," Sullinger said.