Sorting through the Celtics' center picture with Robert Williams (groin) sidelined

The Celtics got mixed news on the injury front Tuesday as they began their second week of preseason work with a lengthy practice at the Auerbach Center.

Romeo Langford (groin) and Daniel Theis (adductor strain) were back taking part in live-action after sitting out Sunday's preseason opener against the Hornets. The same goes for Gordon Hayward, who was battling a  left elbow bruise that forced him to leave the third quarter of Sunday's game with a heavy ice wrap.

"I mean it’s definitely sore today," Hayward said. "I’ve got the arm sleeve on, not just for looks. I think I just fell on it, couldn’t remember exactly when it happened. We took a look at the film, there was kind of one play, it kind of bruised up pretty badly. But it’ll be alright."

The Celtics are still not at full strength yet after those returns however after Robert Williams suffered a tweaked groin before practice even began on Tuesday. He was going to have an MRI as a precaution this week.

“They didn’t think it was anything big, but he wasn’t going full speed or anything when it happened,” Stevens said.

Williams had opened the season as the starting center against the Hornets and struggled in his 10 minutes of action as he was soundly outplayed by Bismack Biyombo in the second half. While there is still plenty of experimentation going on with lineups, Stevens seemed open to the idea of keeping Williams (or another center not named Enes Kanter) in the starting five moving forward.

“I don’t think it’s going to be very complex," Stevens said of the center rotation. "Whoever does their job most consistently and makes those guys around him better will probably play the majority of those minutes. Now Kanter is going to do things, and has some things he does really well that I think is just unique, so he’s obviously going to play. We’re trying to figure out if it’s best with the starting unit or best to bring him off so you can play through him a little more on the block and those type of things. And that’s probably the case if we continue to start all those guys on the wing.

"We’ll see how that goes over the next couple of weeks. I think Theis, again, having been here, things come so easily to him. I think Vincent played as well as anybody the other night and obviously Kanter brings some unique things to the table. When we get Rob back, I’m not worried about Rob having a struggle or two. He’s really pressing to try to play hard, which I think is a good thing.”

BSJ Analysis

Stevens is not one to throw criticism at any of his players so his positive remarks about everyone here is no surprise. However, it's evident that Williams' injury could be a serious setback for the second-year center when it comes to opportunity. The 21-year-old has been plagued by knee and leg issues throughout his career that impacted his availability last season at times. With a hungry supporting cast behind him that has more experience (Theis) and size (Poirier, Kanter), there is going to be a chance for Poirier or Theis to earn some reps as a starter in the coming days. If either of those two shows a good fit with the rest of the starting group we saw on Sunday, Williams' shot to start may be sidelined for the time being.

On paper, the Celtics would love Williams to earn the starting job based on his potential, contract and the fact he doesn't need the ball on offense in a wing-heavy lineup. However, there's a reason why Danny Ainge jampacked this roster with alternatives this summer. It's hard to judge too much from one game but Williams clearly needs some seasoning from a positioning and strength perspective right now to hold his own against NBA-caliber bigs. Poirier only played six minutes on Sunday but showed a lot more promise in that area when it comes to the basics.

“Vincent was good. I thought he played hard, he was in the right spots defensively, he read our coverages well. I thought when he was in I felt good about our pick and roll defense which is a big deal," Stevens said.

If Stevens is committed to bringing Kanter off the bench (which is probably a good idea to avoid being attacked by opposing defenses alongside Kemba Walker in the pick-and-roll), then a healthy Poirier or Theis probably have the inside track now to a starting job at the beginning of the year. Theis won't be an ideal option against massive post threats like Joel Embiid but a rotating starting big depending on the matchup may be the answer if the C's are looking for a more defensive-minded big than Kanter most nights against the starting opposition. For now, Williams has to prove he's worthy of that spot, but it's going to be tough for him to prove it from the sidelines.