49ers RB Raheem Mostert out eight weeks, CB Jason Verrett done for season

The San Francisco 49ers defeated the Detroit Lions in Sunday's regular-season opener but suffered a pair of losses in the process.

According to ESPN, San Francisco head coach Kyle Shanahan told reporters Monday that running back Raheem Mostert is going on injured reserve and is expected to be sidelined eight weeks with chipped cartilage in his knee. A player on IR is eligible to return after missing a minimum of three games, but that clearly won't be an option for Mostert this time around. 

Additionally, Shanahan unveiled that cornerback Jason Verrett tore his ACL and is out for the season. Shanahan said shortly after Sunday's win that it was feared Verrett would be lost for the campaign with that exact injury. 

Mostert had 20 yards on two carries in Sunday's outing before he suffered the setback. Rookie ball-carrier Elijah Mitchell took advantage of the opportunity and extra touches and gained 104 yards with a touchdown on 19 attempts. 

Injuries limited Mostert to eight games last year.

The Niners play at the Philadelphia Eagles (1-0) this coming Sunday.