Coach Mike Krzyzewski said the good news for the Blue Devils is that Jefferson's fractured bone will not require surgery.
"He'll be in a cast -- from now until the time after [Duke plays Utah on Saturday] and they go home -- so it's protected," Krzyzewski said. "When he comes back on [Dec.] 26th, the cast will come off. He'll be in a boot and be re-examined to see how far along he is, not that we expect him to be back. He'll be out for an indefinite period of time."
Jefferson's injury is a major blow to an already thin frontcourt.
A 6-foot-9 forward, Jefferson was having a career season, averaging personal highs of 11.4 points and 10.3 rebounds. Krzyzewski said his vocal leadership on the floor would be one of the areas in which the team misses him the most.
Jefferson got hurt while going after a loose ball. While he is out, Krzyzewski said the Blue Devils would modify their practices.
"We can absolutely have no contact in practice," Krzyzewski said. "The worst thing that can happen to us is to lose a guy on an injury in practice."
Duke used a seven-man rotation against Georgia Southern. Freshman forward Brandon Ingram took over Jefferson's role at power forward, and freshman guard Luke Kennard made his first start of the season. Ingram responded with his first double-double, posting season highs of 26 points and 14 rebounds.
"That four position, we've had a scorer there since Danny Ferry," Krzyzewski said. "We're the ones that invented that. We've been doing that for almost 40 years."
When Ingram subbed out of the game, Krzyzewski opted against using a lineup of freshman forward/center Chase Jeter and senior center Marshall Plumlee. Instead, the Blue Devils played with four guards.