Claudio Ranieri has demanded that his side bounce back from the 3-0 humiliating defeat to Chelsea on Saturday.
Diego Costa, Eden Hazard and Victor Moses all found the net respectively to down the Premier League champions at Stamford Bridge.
And Ranieri - who managed Chelsea between 2000 and 2004 - is hoping his Foxes imrove when they take on FC Copenhagen in the Champions League on Tuesday.
"It's clear when you come to Chelsea you know they are big team and the attention has to be at the maximum," the Italian told Sky Sports.
"We made mistakes, and we tried to react - the second half was much better - but then they scored the third goal. Now we have to react again in time for Tuesday.
"I've forgotten the first half because we were so poor. They played well but we conceded everything. The truth is our approach was not good and it was very easy for them.
"I didn't recognise my players in the first half, but I will speak to them. At least it is better that it is happening now than the end of the season.
"We now have a tough game - Copenhagen are a good team. We have to react or it will be another bad game."
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