The results of the MRI performed on Deng's calf revealed a Grade 1 or 2 strain.
"He's got a little calf issue," coach Vinny Del Negro said. "A little strain. We'll see how he feels, but I think he's going to be out for a little bit, but I don't know how long."
Del Negro isn't sure if Gibson will be able to play Thursday against the Magic.
"We have our top guys out, that's what makes it tough," Del Negro said. "We just got to try to find a way to weather this storm and find a way to get better defensively. Get back to where we were defensively. Holding teams where we liked them.
"That's the way we won games early. So, obviously, we're a different team than we were with our personnel and things, but we have to continually get better and find ways every day in practice. No one's going to feel sorry for you. We got a tough stretch right now, but we got to find ways to keep ourselves in games and give ourselves an opportunity at the end. And try to steal one of two and take them one at a time."
Nick Friedell covers the Bulls for ESPNChicago.com.