"It's too early to tell, but it doesn't look good," one source inside the organization told NFL Media's Aditi Kinkhabwala.
A Monday morning MRI on Bell's hyperextended right knee revealed no ligament damage, per ESPN's Adam Schefter, who reported that it will be "difficult" for Pittsburgh's star running back to suit up for this weekend's AFC playoff bout with Baltimore.
Bell exited Sunday night's 27-17 win over Cincinnati after Bengals safety Reggie Nelson hit him low. It looked ugly on replays, with Bell immediately grasping for his knee in pain. He was able to jog off the field, but Dale Lolley of the Observer-Reporter noted that Bell could "barely walk" around the facility on Monday.
No injury will be watched more closely this week, considering Bell's immense impact on Pittsburgh's offense. The NFL's second leading rusher -- with 1,361 yards on the year -- ripped off a franchise-record 2,215 yards from scrimmage in his second season.