Detroit Lions running back D’Andre Swift (32) runs as San Francisco 49ers defensive back Jason Verrett (2) makes the tackle in the first half of an NFL football game in Detroit, Sunday, Sept. 12, 2021. (AP Photo/Duane Burleson)

Injuries decimated the San Francisco 49ers last year and if week one is any indication, things may be just as bad in 2021. When Jason Verrett went down with an injury to the ACL of his right knee yesterday, everyone feared the worst. Those fears were realized when Kyle Shanahan confirmed on Monday that Verrett had indeed torn the ligament and would be out for the season.

The bad injury news didn’t end there. Shanahan also announced that running back Raheem Mostert suffered chipped cartilage in his knee and will need surgery. Mostert will be placed on injured reserve and is expected to miss at least the next eight weeks.

The depth of the 49ers’ secondary was a concern throughout the offseason, and the loss of Jason Verrett for the year could become a pivotal moment for this season.

With Verrett out, San Francisco needs Emmanuel Moseley to return healthy and play as he did in 2019 when he replaced Akhello Witherspoon. Unfortunately, Moseley has been dealing with knee injuries of his own after getting rolled up on during the 49ers final practice before Labor Day weekend.

If Moseley is unable to go, the 49ers will be forced to go with veteran options Josh Norman or Dontae Johnson or turn to rookie Ambry Thomas. The 49ers defense uses a good deal of man-to-man coverage, something that is neither Norman nor Johnson’s strong suit while being a strength of Thomas.

Regardless of who replaces Verrett, the 49ers’ defensive line will need to step up. San Francisco’s philosophy has been to build the defense from front to back, and this will be put to the test over the next 17 weeks.

The loss of Mostert is a blow to the offense, but the 49ers running back room has shown the ability to step up. Trey Sermon will be among those expected to fill in for Mostert. The third-round draft pick spent training camp working with the starters before being a surprise on the inactive list for week one.

Mostert was replaced on Sunday by another rookie, sixth-round pick Elijah Mitchell. Mitchell stood out in his NFL debut, becoming the first rookie running back in 49ers history to gain over 100 yards in a season opener. JaMycal Hasty played 16 snaps and had two touches, scoring a three-yard touchdown on his lone rush and picking up 15 yards on reception to convert third and ten early in the fourth quarter.

Look for the 49ers to make additions at cornerback and running back in the coming days.