Kansas City Chiefs quarterback Brady Quinn left Sunday's 26-16 loss against the Oakland Raiders with a head injury.

In the first quarter, Quinn was picked off by Matt Giordano and took a hard hit on the play. He also took a hard smack when he was sacked by Rolando McClain on the play prior to the interception.

It was announced after halftime that Quinn would not return to the game.

Matt Cassel, who had lost his starting job to Quinn after a poor start to the season, along with a concussion he suffered three weeks ago against Baltimore, took over under center after Quinn left.