The defender was taken off at half time during Wednesday's 2-0 triumph in Croatia, but Ancelotti is confident that he will be fit for Saturday's trip to Nancy.
"Alex had knee pain, nothing too serious but he could not continue. This is why [Zoumana] Camara entered," said the Italian. "We did not want to take any chances. I think he will be available against Nancy."
PSG's victory over Zagreb has lifted them up to second in Group A, three points behind leaders Porto.