Johnson has been suffering from a stomach bug and struggled through the goalless draw with Aston Villa at the weekend.
Koumas, who was not in the squad against Villa, has pulled out because of "personal reasons."
Johnson and Koumas Out
Johnson has been suffering from a stomach bug and struggled through the goalless draw with Aston Villa at the weekend.
Koumas, who was not in the squad against Villa, has pulled out because of "personal reasons."