Kolb suffered a concussion in the Bills' preseason loss to the Washington Redskins on Aug. 24. The Bills are proceeding as if Kolb's concussion could be career-ending, but he still is undergoing tests.
The Bills signed Kolb in the offseason to compete with rookie EJ Manuel for the starting quarterback job. Manuel's status for the season opener on Sept. 8 against New England is uncertain because of his ailing left knee.
Also Friday, the Bills released quarterback Matt Leinart.
"Tough game. Tough situation. No excuses. (Thank) you to the Bills organization!" Leinart wrote Friday, before deleting the tweet
Information from The Associated Press was used in this report.