Mostert (knee) won't practice Wednesday, Jennifer Lee Chan of NBC Sports Bay Area reports.
Meanwhile, fellow running back Tevin Coleman is a candidate for injured reserve, with a potential prognosis of about four weeks on the sideline, per Nick Wagoner of ESPN.com. Coach Kyle Shanahan considers Coleman's knee sprain to be "worse" than Mostert's, which backs up the 49ers' assessment that the latter will avoid an extended absence. Assuming both Mostert and Coleman are out Sunday versus the Giants, the team's backfield options may be just Jerick McKinnon and Jeff Wilson this weekend.