Mostert leaves practice with back issue

49ers RB Raheem Mostert left Wednesday's practice with "apparent back pain," according to insider Cam Inman. "Mostert winced as he reached the sideline and was checked on by trainers, then watched most of the remaining plays from a knee," Inman adds. We'll see how serious of an issue this ends up being. Mostert, of course, has struggled staying healthy over the past 3 seasons -- although he's never had back trouble.