NAPA, Calif. (AP) — Oakland Raiders wide receiver Louis Murphy is being held out of training camp practice with a concussion.

Murphy says he got hurt when he was kneed in the helmet by teammate Nnamdi Asomugha during practice Friday. He has a bad headache and missed practice Saturday.

Coach Tom Cable says Murphy will not return until he passes a series of tests that shows he has recovered. Murphy says he has never had a concussion before.

Murphy is being counted on heavily in his second year in the NFL. He led all Raiders wideouts with 34 catches for 521 yards and four touchdowns as a rookie last season.