DAVIE, Fla. (AP) -- Miami Dolphins middle linebacker Zach Thomas will sit out Sunday against Buffalo because of migraines -- the fourth game he has missed since a concussion in September.

The setback raised anew questions about whether the 34-year-old Thomas will return this season.

He hasn't played since suffering whiplash in a car accident driving home from the Dolphins' loss to New England on Oct. 21, which led to recurring migraines. Thomas also missed two games in September following the concussion.

He participated in full-contact drills Thursday but was held out of practice Friday and ruled out for the game.

"That's the recommendation of our medical staff," coach Cam Cameron said. "He had a good practice yesterday, but as we're finding out in these situations, one day isn't always indicative of the next day. ... He came in this morning and things were not quite the same."

The seven-time Pro Bowl linebacker has been slowed by migraines and concussions in the past, but Sunday's game will be only the 17th he has missed in a 12-year career.

Injuries have been a big factor in the Dolphins' 0-8 start, with the defense particularly hard-hit.

In Thomas' absence, the Dolphins will again move Channing Crowder from outside linebacker to the middle, and Derrick Pope will again start on the outside.

"I grew up a Zach Thomas fan," Pope said. "You just say his name and it brings chills. ... So to see him going through this right now, it hurts. But that's where I come in and try to make sure the defense doesn't skip a beat."

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