For Oakland, the move is encouraging but is a sign of work to come. Carr is just one of many dominoes in play for general manager Reggie McKenzie, who now must figure out how to retain Khalil Mack. Quite possibly the best defensive player in football, Mack is under contract through 2018 thanks to the club option. Wide receiver Amari Cooper is on the distant horizon, while standout guard Gabe Jackson is making his case for something in the near future in a market that has become very expensive of late.