The Blues face Swedish club Malmo in the Europa League last 32 on Thursday in their first match since the 6-0 defeat – their heaviest in 28 years.
Sarri’s side have also lost to Bournemouth and Arsenal in recent weeks, slipping to sixth in the league.
“It’s not easy to play after losing 6-0,” said Sarri.
“But we have to play and we have to play well. We want to win. We want to react immediately.”
Sarri said the team spoke for an hour at the training ground on Monday, having conceded four goals in the first 25 minutes against City.
“It’s better to work, to react on the pitch,” he said.
“The last match wasn’t a problem of motivation. In the first four or five minutes we started well. We were not able to react.
“We conceded and then weren’t able to do anything.”
Sarri added he had not spoken to Chelsea owner Roman Abramovich following the defeat.
“Not this week, not in the last three weeks,” he said.
“I would like to speak to someone of the club, not necessarily the owner. I speak to [director] Marina Granovskaia and for me that is enough.”