"We'll probably make that call tomorrow," McCarthy said.
"I shot downhill, fast, trying to get a shot on him, and he cut back," Barnett said after Sunday's game. "So I tried to cut, and it was just bad footing."
"I definitely could've done better," Bishop said after the game. "The touchdown I gave up was bad."
However, Bishop said he was "definitely" comfortable with the possibility of having to take over Barnett's starting role.
Barnett said after Sunday's game that he was "just hoping for the best," but McCarthy said medical tests Monday morning revealed the severity of the injury. Surgery hasn't yet been scheduled, and McCarthy did not provide details of Barnett's rehabilitation timeline.
Barnett, a first-round draft pick in 2003, was named a Pro Bowl alternate last season after receiving a contract extension through 2012.
Barnett forfeited his paycheck for the first game of this season under the NFL's personal-conduct policy, after reaching a plea bargain deal for his role in a disturbance at an Appleton nightclub last year. The NFL also has fined Barnett a total of $15,000 this season for a pair of hits deemed illegal by league officials.
Copyright 2008 by The Associated Press