Keenum (concussion) has been ruled out for Sunday's game at Buffalo, JP Finlay of NBC Sports Washington reports.
Keenum practiced on a limited basis throughout the week, but Dwayne Haskins got most of the reps with the first-team offense. With Keenum not being able to clear the concussion protocol, Haskins will step in for his first NFL start, with Colt McCoy serving as the backup. It isn't clear if Keenum will return to the starting job once he's cleared of the concussion.