Mourinho turned his wrath on the fixture schedulers after his side scraped through to the quarter-finals of the Europa League.
Juan Mata scored the only goal of a tight second leg at Old Trafford to give Mourinho's side a 2-1 aggregate victory.
The game came three days after 10-man United lost in the last eight of the FA Cup to Chelsea and ahead of a Premier League trip to Middlesbrough at midday on Sunday.
Mourinho told BT Sport: "I was afraid of extra-time and I knew I had Marcos Rojo in trouble, so it was a difficult game.
"It is difficult to play Monday night with 10 men, it is difficult to play now and it is difficult to play on Sunday at 12 o'clock so we have lots of enemies. Normally the enemies should be Rostov but we have a lot of enemies.
"We have lots of things going against us and we will have to fight and we will probably lose on Sunday. Fatigue has a price."