Black is missing Monday's practice due to an adductor injury, Nick Wagoner of ESPN.com reports.
Black now is one of three 49ers running backs tending to a health concern -- also, Jordan James (ribs) and Isaac Guerendo (pectoral) -- leaving Patrick Taylor, Sincere McCormick and Khalil Herbert to handle reps behind No. 1 option Christian McCaffrey. A third-round pick in this year's draft, Black will have a prime chance to compete for the direct backup role once he's healthy, especially since James is out indefinitely with fractured ribs.