Knighton was limited in practice Friday because he is dealing with cluster headaches that held him out of a game two weeks ago. Robinson missed last week's game with a bad shoulder.
Knighton sat out practice Thursday to see a specialist for what coach Jay Gruden called ''a follow-up'' visit. Said Gruden: ''Hopefully, they did something to give some relief to his headaches.''
Backup safety Trenton Robinson will miss Sunday's game with a hamstring injury.
Washington is 4-5. Carolina is 9-0.