The centre-half misses the trip to the Britannia Stadium after picking up a one-match ban for a sending off in last Saturday’s 1-1 draw at home to Sunderland.
Koeman admitted it is not ideal to be without the skipper, but is optimistic they can cope without him this weekend.
"He's really a high personality for the team and shows always the ambition, the spirit to the rest of the players, but we have to take it. It's one game banned and, ok, next week he's back, but we have enough players and enough quality to replace José.
Koeman added: "We have not really a lot of possibilities to change defenders, but we have Maya [Yoshida] as a possibility, [Matt] Targett is a possibility and we will put the best for this Saturday."