Mourinho is expected to make changes to his side to give them a chance of qualifying for the Champions League.
But he has warned there can be no more complacency in his star-studded squad.
He explained: "Sometimes, when you win a lot of times, players forget why they win. Probably they forgot why they won against Schalke, Arsenal, and Manchester City. When you win three, four, five matches they forget why they won and think they win just because they are good.
"If you think like that, you're in trouble. You can never forget why you are winning matches. Maybe we forgot."