Maurizio Sarri admitted his Chelsea players could not explain the reason for their second-half collapse against Bournemouth during a lengthy post-match inquest in the away dressing room at the Vitality Stadium.

Four second-half goals condemned Chelsea to a 4-0 defeat -- their worst in the Premier League since 1996 -- and Sarri took the unusual step of sending his backroom staff out of the dressing room to speak to his squad alone for almost an hour before conducting his mandatory post-match media duties.

When he finally appeared at his news conference, Sarri said he wanted his players to tell him why they fell apart so spectacularly after the interval, conceding twice to Josh King while the superb David Brooks and Charlie Daniels also found the net.

"In that moment I wanted to talk with them alone, without anybody else," Sarri said. "I needed to understand. It's impossible to play in such a different way between the first and second half. I don't understand why. I don't know exactly. I want to try again tomorrow because we want to solve the problem.

"It's very difficult to have an idea of the performance. We played very well in the first half. In the second half we conceded the [first] goal after two minutes and stopped playing. In the offensive phase, we played not as a team, but as individual players, and did not defend. It's hard to understand why.

"What I saw in the first half, there was the possibility to solve the problem. We had 43 minutes still to play, so we could solve the problem. But not with that kind of reaction. So it's very difficult for me to understand why. I wanted to try to understand after the match.

"I spoke with the players immediately after the match, but it's very difficult also for them to say why. So I have to try again tomorrow because I need to understand why, because I need to solve this problem."

Bournemouth were well prepared by Eddie Howe, defending deep to stifle Eden Hazard and Gonzalo Higuain on his Premier League debut and carving Chelsea open repeatedly with fast and fluid counter-attacks.

Man of the match Brooks did a similar marking job on Jorginho to the one executed successfully by Richarlison, Dele Alli and Aaron Ramsey earlier in the season, while Howe afterwards revealed he had instructed his players not to worry if Chelsea had the ball.

Asked if his system has become too predictable and easy to play against, Sarri replied: "No, we are not an easy team for teams to play against. I think we played a very good first half, with some problems in the offensive phase.

"We had many players with the back to the opposing goal, so we need more movement without the ball otherwise, for the striker in this team, it's really a big problem to play. It's difficult for the strikers and wingers to find spaces, so we need to improve. But we played a good first half."

A torrid night for Chelsea also yielded the first signs of significant supporter discontent with Sarri's methods, as loud chants of 'You don't know what you're doing' rang out from the away section when Higuain was substituted for Olivier Giroud in the 65th minute.

"We have only to say sorry to our fans," Sarri admitted. "We can lose, of course, in every match, but not in this way. We need to solve the problem. We need to understand where the problem is."

Asked if he now feels his job is under threat, the Italian replied: "No, I feel frustrated. Not under pressure. I don't see ... I didn't see the signal of my work. So I am frustrated."