As Chelsea prepare to welcome former boss Jose Mourinho back to Stamford Bridge, head coach Antonio Conte said the London club remain scarred from last season's failed title defence.
Chelsea coasted to Premier League glory under the guidance of Mourinho in 2014-15 but things quickly turned sour the following campaign as the team flirted with relegation before the Portuguese manager departed in December last year.
The Londoners went on to finish 10th, ultimately missing out on European qualification, something that still haunts Chelsea, according to Conte ahead of Manchester United's visit on Sunday.
"When there are these types of season - very bad seasons, because we finished 10th in the table - it's normal that something remains in the players," said Conte.
"In their minds. In their heads. In this situation, the risk is to lose the confidence. For this reason, I continue to repeat: this new season for Chelsea is very important.
"Also, it's very difficult because you must change what happened last season, and that's not easy. The only way we have to change is to work, to work very hard, together with the players, the club and the fans. It won't be easy to cancel a bad season like last season."
United travel to Stamford Bridge after playing out a goalless draw with in-form Liverpool on Monday.
Mourinho's men set up to stifle and frustrate Liverpool throughout at Anfield, a display criticised by fans and pundits.
Conte insisted he would never send out his team to play for a draw, with maximum points and entertainment the focus.
"It's important to win, but for me also it's important to win in the right way," Conte said.
"I've won games in the past with other clubs but I wasn't satisfied with the performance. When you win it's important to put in a good performance for your fans, to show also our work. I think to win is important but it's important also to play good football, to play with good intensity, to show always the will to win, the passion.
"For me, that's important. You have to start every game trying to win, and I transfer these thoughts to my players. Always. Whether we are playing at home or away. You must start the game with only one target: to win. Not to play for a draw. I don't like this. It's not football."