Each of the club's three away fixtures in the group stages of the Champions League this season falls on a Wednesday night and is then followed by a Premier League game at 3pm on Saturday.
According to The Telegraph, Mourinho believes that the relative lack of preparation afforded to his side gives United a "disadvantage" over their rivals in the race for the title.
As things stand, United have a total of 196 hours between away Champions League games and their next league fixtures, whereas Liverpool have 321 hours, Tottenham Hotspur have 290 hours, Chelsea have 250 hours and Manchester City have 219.
As a result of the scheduling, United will welcome rock-bottom Crystal Palace to Old Trafford this weekend less than 60 hours after completing a 1,600 mile journey home from CSKA Moscow.
United are currently second in the Premier League table, level on points with leaders City.