Chelsea were beaten 2-0 by Manchester United at Stamford Bridge in another disappointing display.
Manager Sarri came under attack from Chelsea fans in the second half with calls from him to be sacked.
At the final whistle, the Chelsea players were booed off the pitch by the home fans.
And Sarri now faces a battle to raise spirits before Thursday’s Europa League clash with Malmo.
Speaking to the BBC after the match, Sarri claimed Chelsea were unfortunate to lose but needed to be more aggressive.
“Tonight we were unlucky because we played a very good first half and at the end of the half the score was 2-0,” he said.
“We gave them a few opportunities. We played confusing football in the second half.
“After the first half it wasn’t easy to play with that score. We played very good first half.
“I feel the pressure for results of course, not about something else.
“We have to work, we have to speak, we have to find more aggression and determination in both boxes.”
Pedro started the match but failed to impose himself on the Manchester United defence.
But he has called on people to remain calm despite their “difficult situation”.
He said: “It was a big opportunity for us to stay with the supporters but now it is a difficult situation. A difficult day for us.
“In the second half it was so difficult for us. Now the most important thing is to stay calm and prepare for the final on Sunday and the Europa League.
“We have to believe in ourselves and this team, we have great players.”