The ban means that Rooney will miss all three of England's group stage matches, and Capello is faced with the decision of taking Rooney for the knock-out stages, or replacing him altogether.
"Fabio Capello has got to take another player in place of Wayne Rooney," Cohen told The Mirror.
"You can't have a player that he can't use mooching around the tournament because that would be a total waste of time.
"For Capello, this was the last thing he wanted. It's a really, really bad situation for him. But we've got to learn from past lessons. You can't take players who are unable to play – whether they're carrying injuries or are suspended."
Cohen made 37 appearances at right-back for England, and was part of the 1966 World Cup winning squad.