Breida will have an MRI on Monday to evaluate what's believed to be a mid-to-high ankle sprain, Matt Maiocco of NBC Sports Bay Area reports.
Breida was removed from Sunday's 28-18 loss to Arizona in the first quarter and never returned, later leaving the stadium with a protective boot over his injured foot/ankle. Initial X-rays came back negative, but he still needs an MRI to test for ligament damage. With the 49ers going nowhere and Breida banged up since the preseason, a cautious approach would make a lot of sense. The second-year back does have an extra day to recover in Week 6, as the Niners are traveling to Green Bay for a Monday game. It won't come as any surprise if the team adds another running back to help 29-year-old Alfred Morris and special teams ace Raheem Mostert.