Mack (coach's decision) is inactive for Sunday's game against the Jaguars in London, Aric DiLalla of the Broncos' official site reports.
Though Mike Boone's (ankle) recent move to injured reserve opens up a spot for a third running back in Denver, Mack looks like he'll have to wait until after a Week 9 bye to make his Broncos debut after he was signed off the 49ers' practice squad Monday. Mack's lack of utility on special teams may have been a factor in him sitting out in London, as the Broncos are opting to keep Devine Ozigbo active in London as the No. 3 option behind Melvin Gordon and Latavius Murray.