Mostert (quadriceps) is fully healthy and has added nearly 15 pounds of muscle in the offseason, Matt Barrows of The Athletic reports.
Mostert is competing for a spot on the 53-man roster in San Francisco's crowded running back room. News of Jerick McKinnon (knee) suffering a setback in his recovery could increase Mostert's chances of sticking around, though he'd remain behind Tevin Coleman and Matt Breida on the depth chart. It remains to be seen whether he'll suit up for Thursday's preseason-finale against the Chargers.