Joe Williams

Shanahan reportedly lobbied the San Francisco front office to draft Williams in the fourth round last year, perhaps believing the Utah product could push Carlos Hyde for a starting job. Instead, Williams failed to make an impression during the offseason program and training camp, ultimately landing on injured reserve after he injured his ankle in the final week of the preseason. The 24-year-old made a full recovery before the end of his rookie campaign, but the 49ers didn't bring him back from injured reserve, sticking with Hyde and undrafted rookie Matt Breida in the backfield. Hyde has since been replaced by Jerick McKinnon, who signed a four-year, $30 million contract that includes $11.7 million guaranteed. Williams may have a chance to compete with Breida for the backup role, but a roster spot isn't guaranteed. The Niners carried special teams ace Raheem Mostert (knee) as their No. 3 back last season, and they also brought in 2017 fifth-round pick Jeremy McNichols to compete for a job.

This doesn't necessarily mean the injury is serious; the 49ers may just be glad to keep their 2017 fourth-round pick without having to use a spot on the 53-man roster. Initially hyped as a candidate to earn a major role, Williams struggled with ball security and learning the offense throughout training camp and the preseason, while undrafted rookie Matt Breida proved to be a quick study. Breida presumably will enter the season as Carlos Hyde's top backup, with Raheem Mostert holding the No. 3 spot on the depth chart. Williams is still an intriguing asset in dynasty leagues, as Hyde can become a free agent after the season.