While Benitez will lose only one senior player - Mali midfielder Mohamed Sissoko - he is concerned that the tournament runs during January and February.
He said: "They must try to find a proper schedule for all the clubs and organise things in a different way."
A number of English sides will lose players during the three-week competition and Benitez said: "I would like to have an advantage but I do not know. Some teams might sign five or six players."
On whether the Nations Cup would prevent him employing many African players, he said: "We try to sign the best players and the best are normally internationals.
"You cannot analyse a situation like this. You sign someone for four or five years, not six weeks."