Four-time Pro Bowl center Travis Frederick has been placed on the non-football illness list by the Dallas Cowboys because of a nerve condition that has kept him from playing this season.
The team also placed receiver Terrance Williams on injured reserve because of a foot injury.
Those moves Saturday cleared two spots on the active roster before Sunday's game at Houston. One will be filled when defensive tackle David Irving returns from a four-game suspension for violating the NFL's substance abuse policy, but the team said he didn't make the trip and wouldn't play against the Texans.
Frederick was diagnosed during the preseason with Guillain-Barre syndrome. The Cowboys initially kept him on the active roster, but now he will miss at least eight more weeks. He could possibly return the final month of the regular season.
Williams will also miss at least eight weeks.
