Mourinho also said that Costa will play no part against Maribor on Tuesday evening.
"The only thing I can say is after Arsenal he went to national team, he played two big matches against Slovakia and Luxembourg and became in condition where he's not able to play for this club," Mourinho told reporters after the game at Selhurst Park.
"I think he'll be in great condition in mid-November to be back for the national team. That's for sure. Our medical department will take good care of him and he'll be in perfect condition.
"He will play for me when he's got free time from the national team."
The £32m signing has scored nine Premier League goals in six appearances this season.