Alfie Mawson is not expected to feature for Fulham before the end of the month.
And boss Slavisa Jokanovic believes Mawson will need time to build up his match fitness.
Jokanovic explained: “He won’t be ready yet. We must wait two or three weeks for him to start working with us and I don’t expect he can help us before September.”
Mawson is among six major summer signings made by Fulham, who have also brought in Jean Michael Seri, Aleksandar Mitrović, Maxime Le Marchand, keeper Fabri and former Chelsea man Andre Schurrle.
Jokanovic suggested after the Celta Vigo game that he would like to make up to three more signings before Thursday’s transfer deadline.