Mourinho has decided to move Christmas Day training to Old Trafford next month.
He is planning to hold a 5pm session at the stadium, rather than the usual Carrington base, ahead of the Boxing Day visit of Burnley.
The Sun reports that has effectively wrecked the day for another 50 or so members of staff who will have to be on duty, rather than spending most of the day with their family.
A training session at Carrington demands around 20 workers.
Moving it to Old Trafford means up to 70 must be in attendance for matters like extra security and preparing the pitch for the following day's fixture.