Jason Campbell sustains head injury

SAN FRANCISCO -- Oakland quarterback Jason Campbell was knocked out of the Raiders' exhibition game against the San Francisco 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."

Campbell sat alone on the bench for the rest of the first half and did not come back to the field in the second half. He was going for tests Saturday night to determine whether he had a concussion. Campbell said he has had a slight concussion once before in his career.

This marks the second straight year that Campbell got hurt in an exhibition game against San Francisco. He got a stinger last year that affected him early in the regular season.

Campbell was 5 for 7 for 74 yards in two-plus series as the Raiders lost the game 17-3. Oakland did not score with Campbell on the field, going three-and-out on his first drive and failing to push it in after driving to the 1 in the second quarter.

Campbell completed a 22-yard pass to Darrius Heyward-Bey that put the ball at the San Francisco 2. Campbell then rolled out on first down and appeared to have Kevin Boss open in the back of the end zone. But Campbell tried to run it in and was dragged down for a 1-yard loss by Patrick Willis.

"One thing we're trying to learn is we have to finish," Campbell said. "The only play I regret from tonight is probably that one. It's a run-first play but at the same time you should try to give him a shot in the back of the end zone."

Michael Bush ran it to the 1 on the next play, but Marcel Reece was hit for a 1-yard loss on third down and Campbell got sacked when he had no open receivers on fourth down.

"We have to finish those drives down there with touchdowns," coach Hue Jackson said. "That's what the expectation is. Again, we didn't get it done."

Campbell then got hurt after Oakland moved the ball into San Francisco territory on the next drive.

Boss also left the game with an injured left knee after getting by a helmet after a catch.

"It's nothing serious, that's for sure," Boss said. "Take a little time to heal up."