Raiders quarterback Jason Campbell was knocked out of the team's exhibition game against the 49ers on Saturday night with a possible concussion after getting kneed in the helmet. Campbell was hurt while scrambling on a play late in the second quarter. He lost the ball on the play and then got hit by defensive lineman Justin Smith and linebacker Ahmad Brooks as he fell to the ground to recover his own fumble. "I tried to go dive on it and caught a knee to the head," Campbell said. "We just have to run some tests and make sure it's not a concussion."