Mason (ankle) did not practice Wednesday, Matt Barrows of The Athletic reports.
Head coach Kyle Shanahan previously said Monday that Mason is headed to injured reserve due to the high-ankle sprain he suffered late in Sunday's 35-10 loss to the Bills. While the transaction has yet to be made, Shanahan reiterated Wednesday that a trip to IR is still likely for Mason, according to David Lombardi of SFStandard.com. The 49ers are set to move forward with a backfield led by rookie Isaac Guerendo, with waiver pickup Israel Abanikanda offering a depth option behind him. The 49ers are also likely to elevate one or both of Patrick Taylor and Ke'Shawn Vaughn from the practice squad ahead of this Sunday's game against the Bears.