Mostert was helped off of the field with an aircast being placed on his foreman.
You can expect the 49ers to place him on injured reserve in the coming days and add someone to their roster.
Mostert, 26, wound up signing on with the Eagles as an undrafted free agent out of Purdue back in 2015. He had brief stints with the Dolphins, Ravens, Browns, Jets and Bears before signing on to the 49ers’ practice squad in 2016.
The 49ers brought Mostert back on a one-year exclusive rights contract this past offseason.
Entering tonight’s game, Mostert had appeared in eight games and rushed for 175 yards on 27 carries (6.5 YPC) to go along with six receptions for 25 yards receiving and no touchdowns.