FRISCO, Texas (CBSDFW.COM) – Dallas Cowboys center Travis Frederick and wide receiver Terrance Williams have been placed the injured reserve list, clearing two spots on the active roster before Sunday’s game against the Houston Texans.

The four-time Pro Bowl center was placed on the non-football illness list because of a nerve condition that has kept him from playing this season.

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Travis Frederick #72 of the Dallas Cowboys (Photo by Ronald Martinez/Getty Images)

The team also placed Williams on injured reserve because of a foot injury.

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One of the roster spots will be filled when defensive tackle David Irving returns from a four-game suspension for violating the NFL’s substance abuse policy.

Frederick was diagnosed during the preseason with Guillain-Barre syndrome. The Cowboys initially kept him on the active roster. Now he will be out at least eight weeks, or seven games, since Dallas has a bye in that stretch. He could possibly return the final month of the regular season.

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