Armstead, 23, appeared to injure his left hand with eight minutes left in the second quarter Sunday against the Redskins. Before his final play, he gingerly placed his left hand on the ground while assuming his four-point stance. After the play, he grabbed his left hand while it hung from his wrist.
Armstead recorded eight tackles and 1.5 sacks through six games before this injury. He is a former first-round draft pick, and he has one season remaining on his rookie contract with the 49ers.
Armstead’s immediate replacement could be veteran Dekoda Watson. In the long term, Ronald Blair will be eligible to return from I.