Green Bay Packers outside linebacker Clay Matthews had another surgery on his broken right thumb.
It's the second procedure Matthews has undergone this season on the thumb.
“They have not given me a timeline on Clay,” Packers coach Mike McCarthy said.
Matthews hurt his thumb again Sunday on a sack of Steelers quarterback Ben Roethlisberger, suffering a similar injury.
Mike Neal and Nick Perry will fill in with Matthews out.
Palmer has been inactive the past five games.
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Aaron Wilson covers the Ravens for The Baltimore Sun