Antonio Conte feels Chelsea are still feeling something of a hangover from their disappointing 2015-16 Premier League campaign.
Conte took over from Guus Hiddink over the summer and believes the deterioration that started under Jose Mourinho - his next managerial opponent on Sunday - is yet to be overcome.
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Chelsea finished 10th last season, missing out on European competition completely, but things are slightly better in terms of position this season __with the Blues sitting in fifth, three points off the top, ahead of Manchester United's high-profile visit to Stamford Bridge.
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He said: "When there are these types of season - very bad, because we finished 10th in the table - it's normal that something remains in the players. In their minds. In their heads.
"It won't be easy to cancel a bad season like last season."
Mourinho's second spell in charge of the club ended in acrimony, __with a section of supporters blaming Chelsea's players for his departure.
But Conte has been keen to keep the subject of Mourinho away from the squad, as much as he could, ahead of the Portuguese's much-anticipated return to the club he led to the Premier League title on three occasions.
He added: "I didn't talk with my players about Jose Mourinho.
"For us, what is important is Manchester United and playing against a team, not against Jose Mourinho.
"When you have a lot of time with a man and you won a lot with him, you love this man. You love this person for the relationship that you were able to create in this time.
"I think the players want to win, but have great respect for him."
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