Steelers rookie right guard David DeCastro was carted off the field after hurting his right knee early into Pittsburgh's preseason game against the Buffalo Bills on Saturday night.
The Steelers announced DeCastro would not return after he was hurt while pass blocking as Pittsburgh faced third-and-8 at its 6-yard line on its second possession.
DeCastro's right leg twisted beneath him after being bowled over by defensive tackle Marcell Dareus.
DeCastro lay in the end zone for a few minutes as trainers worked on his leg. He briefly got up on his own, but was unable to put any weight on his right leg. He took a few hops before trainers stopped him and called for a cart.
The Steelers also lost defensive end Brett Keisel, who hurt his left ankle late in the first quarter.
Keisel did not return for the next series of defensive plays, and the Steelers announced his return was questionable. Keisel was not spotted on the sideline.
Pittsburgh's defensive line is already depleted with defensive tackle Casey Hampton sitting out his third preseason game while coming off right knee surgery.