United are scheduled to travel to Stamford Bridge on October 23 - which is a Sunday following on from the club's Europa League commitments on the previous Thursday.
Mourinho is said to be unhappy that his players will have less than 72 hours recovery time from playing in Europe and is said to regard the clash with his former club as the most important match of the club's season at the stage of the campaign.
He is said to have wanted the game to be moved to the Monday night but it is complicated by the fourth round of the League Cup taking place in the week after.
Mourinho is not afraid of making several changes to his side to prepare for a game that follows on shortly afterwards. Given the likelihood the game will be played on the Sunday, one would not be surprised if there were a few big name players omitted from the Europa League game that precedes United's trip to Stamford Bridge.
However, he will not be quiet in his dissatisfaction, and one would expect his displeasure to be voiced when he gets the opportunity in front of the media nearer the time; possibly when the next round of television fixtures are announced for October onward.