The 49ers' running back room will be without a key piece for the foreseeable future.
He is expected to miss about eight weeks of action.
Since emerging as one of the NFL's most promising young backs during the 2019 campaign, Mostert has had trouble staying on the field because of his health. A calf injury he sustained in the Divisional Round that season threatened to compromise his postseason availability, but Mostert managed to quickly recover. He went on to turn in a memorable 220-yard, 4-TD rushing effort to propel San Francisco to a NFC Championship win and into the Super Bowl for the first time since 2012.
Rather than building off his best pro season, Mostert was limited to eight games in 2020 and logged multiple IR stints due to a nagging high ankle sprain he suffered in Week 2. He finished the year with 104 carries for 521 yards and two touchdowns to go with 16 receptions for 156 yards and a score.
Unfortunately for the 49ers, running back isn't the only position that suffered a big loss. Shanahan confirmed that starting corner Jason Verrett sustained a torn ACL in his right knee and is out for the season. Verrett, the No. 25 overall pick in 2014, has spent the bulk of his career recovering from injuries, a past that involves a couple knee injuries including a previous ACL tear, a torn Achilles, and an ankle injury that notably tanked his '19 season. NFL Network Insider Ian Rapoport reports San Francisco is finalizing a deal with veteran defender Dre Kirkpatrick to add depth to the secondary following the loss of Verrett.
Shanahan also announced linebacker Dre Greenlaw is being considered day-to-day after suffering a groin injury.