Bears cornerback Terell Smith went down with a non-contact injury, and almost immediately, his teammates knew it was bad.
Smith was carted off the field, and the Bears quickly ruled him out with a knee injury.
Smith was covering Kristian Wilkerson when it appeared the ground gave way under his left leg as he tried to cut. Smith grabbed his left knee, while Wilkerson caught the ball from Mike White and took it 25 yards downfield with 1:32 left in the first half.
Before he departed on the cart, Smith covered his face with a towel as his teammates wished him well.
He had two tackles.
Smith played 26 games with two starts the past two seasons, seeing action on 584 defensive snaps and 232 on special teams.
The Bears lead the Bills 28-0 at halftime.