49ers' Joe Williams: Out for a while

49ers coach Kyle Shanahan said Williams suffered a rib fracture that will sideline him for "a while," ESPN's Nick Wagoner reports.

Williams will at least miss Week 1, according to Shanahan, who updated the media regarding his team's injuries Sunday night. The coach continued by saying it hasn't been determined whether Williams will be placed on injured reserve/designated to return, but it's clear the Niners will have to make do without him until further notice. With Williams joining fellow tailbacks Jerick McKinnon (calf) and Matt Breida (shoulder) on the shelf for the rest of the preseason, Jeremy McNichols, Alfred Morris, Raheem Mostert and Jeffery Wilson will split backfield work the next couple weeks.