Albert Haynesworth has a sprained ankle and was unable to make it through a full practice for a second straight day.

The defensive lineman hurt his ankle during Wednesday's practice and didn't take part in team drills Thursday. Coach Mike Shanahan said he hopes the injury isn't too serious and that Haynesworth might be able to return Friday. Washington hosts Houston on Sunday.

Haynesworth played as a backup in the season opener after months of disagreements with Shanahan over offseason workouts, practices and preseason playing time.

Shanahan said backup linebacker Perry Riley is "ready to go" after recovering from a sprained right foot.

Safety Kareem Moore, who has a sprained right knee, appears unlikely to play against Houston.