Clay Matthews has undergone further surgery on his thumb after injuring it again last week.

The Green Bay Packers linebacker missed five weeks earlier this season after breaking his thumb against the Detroit Lions and picked up a similar injury while sacking Pittsburgh Steelers quarterback Ben Roethlisberger in last Sunday's 38-31 defeat.

The 27-year-old had to wear a protective cast that covered his entire hand when he returned from the injury last month.

The NFC North side have not placed a timeline on his return.