49ers' Jordan Mason: To be sent to IR with sprained ankle

The 49ers are slated to place Mason (ankle) on injured reserve, Nick Wagoner of ESPN.com reports.

Mason suffered a high-ankle sprain late in Sunday night's loss to the Bills. After Christian McCaffrey suffered a PCL injury to his knee in the first half, Mason took on a larger offensive role versus Buffalo, finishing with 13 carries for 78 yards. But Mason now is going to be sidelined until at least Week 18. The looming moves of McCaffrey and Mason to injured reserve vaults Isaac Guerendo into the 49ers' RB1 spot. Guerendo will be a priority waiver-wire pickup in fantasy leagues this week. Patrick Taylor likely will be promoted from the practice squad to serve as the Niners' backup running back over the next month.