The Raiders' first defensive drive of the preseason resulted in a forced punt, but it was still a loss for the Oakland defense.
Rookie cornerback Isaiah Johnson took a knee to the helmet from teammate Marquel Lee on a Blake Bortles completion to Rams receiver Michael Thomas and stayed down on the field after the play.
Oakland's team trainers came out to evaluate Johnson and helped him off the field. He did not return to action for the rest of the drive.
Johnson is a fourth-round pick for the Raiders out of Houston appearing in his first action as a pro.
The Raiders have not announced the nature of Johnson's injury.
