Injuries continue to slow development of Bulls big man Wendell Carter Jr.

It isn’t the bruised tailbone that kept big man Wendell Carter Jr. out of the Bulls’ preseason opener Monday that has coach Jim Boylen concerned.

Boylen said it’s the accumulation of injuries Carter has suffered in the last eight-plus months that has him worried.

First it was the thumb surgery that limited Carter to 44 games as a rookie last season. Then there was offseason surgery to repair a sports hernia that had bothered Carter since he was 15. He sprained an ankle during training camp early last week, then suffered the bruised tailbone when he returned.

With Boylen stressing the best ‘‘ability’’ his players can have is ‘‘availability,’’ Carter is falling short in that department.

‘‘I’m concerned,’’ Boylen said. ‘‘I know our defense is better when he’s on the floor. I know our physicality is better when he’s on the floor. So, of course, I am concerned.’’

The good news for Boylen is that Carter’s injury allows the Bulls to look at different lineups and mixes, especially the idea of power forward Lauri Markkanen playing center when they want to go small and have more outside scoring on the floor. Markkanen saw some time there late in games last season and had some solid results.

‘‘He seems to be open more at [center],’’ Boylen said of Markkanen. ‘‘[Power forwards] stick to him pretty good. They crawl into him sometimes. We’ve had situations where they put the [power forward] on our [small forward] and the [small forward] on him, and they try to crawl into him.

‘‘That’s what we are building. Otto [Porter] can go from [small forward] to [power forward]. Thad [Young] can go from [power forward] to [center]. Lauri can go from [power forward] to [center]. I think that makes you more difficult to guard. You are tougher to prepare for, but we also have to see if we can figure it out.’’

The downside to Carter being out, of course, is that it takes time away from him to continue developing.

‘‘I’m just hoping [the bruise] will settle down,’’ Boylen said. ‘‘It’s like a deep bruise to that area, which is taking longer than we hoped.’’

Homecoming

Not only was big man Robin Lopez back in the United Center for the first time since leaving the Bulls and signing with the Bucks as a free agent during the offseason, but he was given a loud applause by the fans.

‘‘He was coachable and he was reliable,’’ Boylen said. ‘‘Just a wonderful guy. Very intelligent guy. And I thought he was a great Bull while he was here during a difficult time.’’

The Bulls said several times late last season that they wanted to keep Lopez, but the numbers in frontcourt didn’t allow it.

‘‘I think we felt [with] our situation with Wendell Carter that it was best for [Lopez] maybe to find another opportunity, which we had no doubt that he would,’’ Boylen said. ‘‘But he was a terrific player for our team. He was a dynamic screener.

‘‘And he was an ‘Amen’ guy in the locker room. When you said something, he’d always give you an ‘Amen’ because he believes in the right things.’’