Al Horford Out, Avery Bradley and Marcus Smart in vs. Bulls

BOSTON – Al Horford’s out, but Marcus Smart and Avery Bradley are in.

The Celtics’ marquee signing from Atlanta was diagnosed with a concussion Tuesday after getting swiped in the face by an anonymous Celtic in practice Monday. Horford returned to practice Tuesday before suffering concussion symptoms and being placed in the NBA concussion protocol.

Horford will stay home for Wednesday’s battle royale against Rajon Rondo and the Bulls as well as Thursday’s premier trip to Cleveland to face LeBron and the Cavs.

While the Bulls will be without shooting swing Doug McDermott with a concussion as well, Horford’s absence for the Celtics comes on one of the toughest back-to-backs of the season.

“Al’s a good player. I was just texting him that we’re gonna miss him tonight. I hope he’s feeling better most importantly,” Avery said. “But it just gives someone else a chance to step up and go out there and play well for us tonight.”

Stevens laid out the play-by-play for Horford’s unpleasant Monday and Tuesday.

“Monday, one of our players swiped for the ball and got him across the face and he felt good Monday. And he felt good Monday night. Slept good Monday night. No symptoms were reported. Came to practices. Went through the lifting and shooting. Felt good and was cleared to practice and then was stopped and removed and went home and then later on in the afternoon yesterday, saw Dr. [Guy] Napolitana and was diagnosed with a concussion. Now he’s in the protocol and he felt better today, but still had some symptoms. And so you have to be 24-hours symptom free before resuming activity. And if that restarts it, if any symptoms come up after that 24 hours once you resume activity, that restarts itself. So we’ll see how he feels tomorrow, but he will not be on the trip [to Cleveland] and he will not play in either game.”

So in Horford’s place will be Tyler Zeller, who has had a roller coaster season so far. Zeller is good for a few impressive pick-and-rolls per game, but is often beat on the glass and misses rotations and cross-cuts on defense. He’ll go against Robin Lopez Wednesday, who he says he will attack head-first to keep Lopez off the glass.

That is a crucial issue after the Bulls won their matchup a week ago on the offensive glass.

“That’s not going to be a one-person thing, that’s going to be a five-person thing,” Stevens said. “[They’re] a really good rebounding team – I thought they played good against us, I thought they were outstanding the next two games. So they’re pretty hot coming in and we’ll have to get them off the glass for sure.”

Bradley and Smart will be those guards responsible for flying in for the boards. Bradley was a big question mark coming into the day, after sitting out practice Tuesday with shoulder soreness.

“I don’t know whether or not it was from sleeping or what, but I got a cortisone shot. I feel good now,” Bradley said.

He had surgery on both of his shoulders in his second season, so any shoulder flare-up is an immediate red flag. But Bradley isn’t worried.

“At first it was [a concern] until we did the x-ray and everything came back – it was perfect. Yeah, my shoulders are good.”

With Smart back and Bradley in, Wednesday could have been a chance to finally see the Celtics’ rotation in tact. But without Horford for at least the two games this week, they can look ahead to hosting Denver Sunday with a potentially full-strength squad.