49ers' Raheem Mostert Out About 8 Weeks with Knee Injury Diagnosed as Torn Cartilage

San Francisco 49ers running back Raheem Mostert will be placed on injured reserve and miss "approximately eight weeks" after suffering torn cartilage in his knee during Sunday's 41-33 win over the Detroit Lions, per Matt Maiocco of NBC Sports Bay Area. 

Mostert left the game in the first quarter after running the ball twice for 20 yards. 

Mostert, 29, appeared to be on the brink of stardom in 2019 after rushing for 772 yards and scoring 10 total touchdowns. His 220-yard, and four-touchdown performance in that season's 37-20 win over the Green Bay Packers in the NFC Championship Game felt like a coronation. 

But both a knee sprain and a high ankle sprain cut his 2020 season in half. In eight games, he rushed for 521 yards and tallied three total touchdowns. 

Before catching on with the Niners in 2016, Mostert played for the Cleveland Browns, Miami Dolphins, Baltimore Ravens and Chicago Bears between the 2015-16 campaigns. The former undrafted free agent also spent time on the practice squads for the Philadelphia Eagles (2015) and New York Jets (2016). 

Injuries have unfortunately plagued Mostert throughout his career. Both his 2017 and 2018 seasons were cut short after he was placed on injured reserve. 

The Niners do have solid depth at running back, however. Rookie Elijah Mitchell had a superb NFL debut in Mostert's stead vs. the Lions, rushing 19 times for 104 yards and a score. JaMycal Hasty also played on Sunday, scoring a touchdown. 

And then there is third-round pick Trey Sermon, who surprisingly was inactive against the Lions but will have the opportunity to work his way back into the good graces of the coaching staff and earn a starting gig. 

For now, however, it would appear as though Mitchell has done enough to be the team's starter going forward.