Blue Devils coach Mike Krzyzewski told ESPN before Duke's 77-75, overtime loss to Utah at Madison Square Garden that the 6-foot-9 Jefferson, who was averaging 11.4 points and 10.3 rebounds per game this season, will be re-evaluated after returning from the semester break Dec. 26.
"It'll be more than a month," Krzyzewski said. "Maybe two. We expect him back later in the season. It's later than earlier."
Jefferson has a cast on his right foot and will travel home to Philadelphia after Saturday's game. Krzyzewski had said that the injury will not require surgery.
Jefferson's injury is significant for a Duke team that is already thin up front. Krzyzewski has moved 6-9, 190-pound freshman Brandon Ingram to power forward.
Jefferson was 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."
Information from ESPN staff writer C.L. Brown contributed to this report.