Sermon (ankle) was placed on injured reserve Saturday, David Lombardi of The Athletic reports.
Head coach Kyle Shanahan seemed to hint this designation was on the table Friday, as the rookie evidently suffered a sprain serious enough to cause him to miss significant time. It's been a disappointing campaign for the Ohio State product, and while Sermon will be eligible to return before the end of the season, it's hard to envision a scenario where the running back emerges as the main ball carrier.