The San Francisco 49ers may be down to their fourth-string running back Thursday against the Los Angeles Rams. Head coach Kyle Shanahan on Tuesday told reporters in a pre-practice press conference that rookie running back Isaac Guerendo wouldn't participate in the

With running backs Christian McCaffrey and Jordan Mason on IR, the 49ers turned to rookie RB Isaac Guerendo to start their Week 14 matchup against the Chicago Bears. Guerendo acquitted himself well in the starting role, but he sprained his foot and may wind up missing Thursday’s game.

Now, it looks as though the 49ers may be down yet another running back, as Isaac Guerendo was forced out of Sunday’s game against the Bears with a sprained foot. While he’s considered day-to-day, San Francisco has a short week this week, and are set to face off against the Los Angeles Rams on Thursday night.