Jefferson's had a sprained right ankle for over a month now, almost incessantly nagging the big man. He's played three regular season games missing time between a couple of them to recover. It seemed like he was finally back on the tracks to full health after playing in two consecutive games, but he must have relapsed.
Without Jefferson, the Bobcats will probably start Biyombo at center once again. Against the Bulls and their defense, Jefferson's absence will be notable. In past years, Jefferson had averaged about 25 points against Joakim Noah.