Raiders had option to sign Khalil Mack to deal cheaper than Bears
Chicago Bears agree to trade for Oakland Raiders star Khalil Mack
Raiders agree to trade former Defensive Player of the Year Khalil
Why the Raiders won the Khalil Mack trade - The Georgetown Voice
Raiders' defensive coordinator defends trading Khalil Mack - NBC
Khalil Mack's Contract With The Bears Has Become Tradable… Should
Poll: Will Raiders Trade Khalil Mack?
Khalil Mack to the Chicago Bears: Why would Jon Gruden and the
Khalil Mack, Amari Cooper trades a reminder of NFL's impermanence
Khalil Mack says he was 'shocked' by trade from Raiders to Bears