Top offseason needs: NFC North

Johnny Knox had a solid season in 2011, but Chicago still needs to upgrade at receiver. Thearon W. Henderson/Getty Images

This continues an eight-part series in which Football Outsiders looks at the biggest holes remaining on each team going into the offseason. Remember, some of these holes might not actually be holes if teams re-sign their players, and other holes will be filled during free agency and the draft.