Rookie Isaac Guerend was promoted to the 49ers' starting running back after San Francisco had to place both Christian McCaffrey and reserve Jordan Mason on IR on the same day.
While the news of McCaffrey taking time out with an injury wasn't a shock, the news of Mason's injury likely caught many off guard.
Mason was placed on injured reserve with an ankle sprain, leaving Gerendo as the top back on the 49ers' depth chart.
Mason was injured Sunday against the Bills and will miss at least four games.
Gerendo had 42 carries for 246 yards, two touchdowns and five catches for 19 yards in 12 games this season.
Mason's injury was a big blow to a 49ers team that was already preparing to miss McCaffrey, who suffered a torn PCL in his right knee.
Niners head coach Kyle Shanahan told reporters Monday that McCaffrey does not need surgery.
“I just feel bad for him,” Shanahan said. According to ESPN. “It's been a really frustrating year for him. He's worked hard to get back here and I think he was feeling really good and was about to take off. He just had a really unfortunate injury last night. He was just as devastated as the others. I know it's been a long time coming, but I'm sure he'll get through this. He's a great player, a great person, and an incredible 49er. And next year, he'll be stronger than ever. He will come back and help us.”
Gerendo was drafted by the 49ers in the fourth round out of Louisville earlier this year, and one of his two rushing TDs came in Sunday's loss to the Bills.
He scored the 49ers' only touchdown Sunday night when he doubled and ran on base in the eighth in the third quarter.
