Boston Celtics rookie guard Marcus Smart did not feel healthy enough to engage in Tuesday's practice session and removed himself early from the team's offday workout.

Smart suffered a strained left Achilles in Friday's loss to the Knicks and sat out Monday's win over the 76ers. The Celtics were hopeful that he would be back on the court for Wednesday's visit from the Orlando Magic, but that now appears unlikely.

"Marcus started off practice, then did not complete it," said Celtics coach Brad Stevens. "I would say that he’s unlikely [versus the Magic], but I don’t know. I haven’t talked to [team trainer] Ed [Lacerte] about it, as far as [Wednesday's game]."

Added Stevens: "[Smart has to] feel right coming off of that. That’s his call. We just want him to feel good, we want him to get better."

Smart missed 10 games last month while recovering from a left ankle sprain and bone bruising. The Celtics eased him back in, but the Achilles strain could be an offshoot of the ankle injury. Stevens wants Smart to return when he feels healthy enough to resume full activities.

"He knows his body. And he knows if he feels right, especially when you’re talking about an Achilles or a knee or an ankle," said Stevens. "It’s a little bit different than an upper-body injury, just because every single movement, you feel it. The directive he was given [Tuesday] was, ‘You see how you feel and you decide.’ Obviously, he didn’t feel great and I don’t think it was anything that happened. I think he just didn’t feel great and pulled himself out. And that’s OK, again, that’s the directive he was given."

Smart is averaging 5.9 points, 2.1 rebounds, 1.5 assists, and 0.9 steals over 16.4 minutes per game in 10 appearances. His biggest impact has been on the defensive end, where his energy and tenacity gives Boston a much-needed boost on the perimeter.

Teammate Avery Bradley endured a similar injury and aggravation last season and said he would caution Smart to tread carefully while working his way back.

"I would tell him, 'Don't come out here trying to be Superman. Just take your time, and when your ankle is ready, it’s going to be ready,'" said Bradley. "I know it took me a while. I had to continue to get that strength back."

Smart and fellow dinged-up teammate Marcus Thornton (calf) were spectators at the end of Tuesday's practice. Thornton suffered a tear in his calf during Sunday's practice and is expected to miss two weeks.

"I was trying to take off and it felt like somebody threw a ball at the back of my calf, or somebody kicked me," said Thornton. "But I looked at the film with nobody behind me, so I knew I pulled it or did something wrong. ... I looked at the film and tried to blame it on somebody, but I couldn’t. Those are the worse ones and very unfortunate."

Thornton said he's feeling better, but admitted the timing of the injury is frustrating given that the Celtics are already without Smart and Thornton was starting to play some of his most inspired ball since arriving in Boston this summer.

"It's very frustrating," he said. "I was just getting into a little rhythm myself and having to deal with this now, it’s very frustrating."