Carell left the TV show near the end of the seventh season to focus on his film career. "The Office" is scheduled to wrap its nine-season run this spring.
E! News quoted several "Office" cast members as saying schedules are being worked out to bring Carell back before the show ends.
However, NBC entertainment Chairman Robert Greenblatt said during the network's Sunday presentation at the Television Critics Association press tour a Carell guest appearance isn't likely because Carell doesn't want to take away from his iconic character's sweet-goodbye two seasons ago.
"I'm hopeful, but I don't think he will be back," E! News reported Greenblatt said. "He left in the way that he wanted that character to leave. ... There's maybe a little Hail Mary pass on a cameo."