Chiefs LB Houston returns to practice

Kansas City Chiefs outside linebacker Justin Houston returned to practice Thursday, but has not been cleared to play, according to the Kansas City Star.

Houston sustained a head/neck injury last Sunday against the Tennessee Titans and was undergoing the NFL's concussion protocol. Coach Andy Reid said Wednesday that Houston's symptoms were gone. He practiced on a limited basis Thursday.

Houston is second in the league with 8 1/2 sacks. If he cannot play Sunday against the visiting Oakland Raiders, Frank Zombo -- who mainly plays special teams -- will likely start.

Zombo, in his fourth year, had a career-high four sacks in 13 games as a rookie in 2010. He played five games in 2011 and seven games last season. He has two tackles this year.