Antonio Conte admits Chelsea risk another season of mid-table mediocrity if they fail to improve their performances after Saturday's humiliation against Arsenal.
Chelsea found themselves 3-0 down inside 40 minutes at the Emirates Stadium as a rampant Arsenal capitalised on a series of defensive mistakes, and the visitors failed to register a shot on target until the 82nd minute.
The result was Chelsea's second loss to a Premier League top-four rival in a week after last Friday's 2-1 defeat against Liverpool at Stamford Bridge, leaving them eighth in the table after six matches.
A defence that has conceded 13 goals in eight games in all competitions is a particular cause for concern. Conte, who was named Chelsea head coach this summer and tasked with reviving the team's fortunes after the most disappointing season of the Roman Abramovich era, recognises the scale of the challenge ahead.
"Today we understood -- me first, then the players -- that this league is very tough," Conte said. "We must improve a lot of if we want to stay up [at the top] and not in the middle of the table.
"But my message is not important. The most important message is the one that arrives on the pitch. We must all understand this message, and find very soon the right solution to improve.
"I don't sleep, sure. I don't sleep. This is normal. After this game, this defeat, it's normal for me not to sleep. Not only tonight, but for two nights. When I don't sleep, I reflect. And it's important to reflect.
"I got angry at half-time but I prefer to keep my words. There are rules in the dressing room. Sure I was angry but my players were also angry. We were not satisfied with our game, with our performance.
"I have to find the solution very, very soon because against Arsenal we played a very bad game."
Gary Cahill gifted possession to Alexis Sanchez for Arsenal's 11th-minute opener while Cesar Azpilicueta, Eden Hazard, N'Golo Kante and David Luiz all made high-profile errors for the goals that followed, but Conte resisted the temptation to single out any of his players for public criticism.
"I don't want to talk about defenders, midfielders or strikers," he added. "Because I think we lose and we win as a team.
"I think that when you want to win, you must have a good balance. When you attack and when you defend. I think that this is the right way if you want to win. If you don't, you have up and down, up and down.
"It's important to work together in defensive situations and to work together in offensive situations. Not with only strikers, wingers and midfielders in offensive situations. Or with only defenders in defensive situations.
"No, we must work together. We can improve a lot. It's important to understand this and to try to work together."