Chelsea boss Maurizio Sarri locked his backroom staff out of the changing rooms after defeat to Bournemouth but admitted an almost hour-long inquest with his players left him none the wiser as to how his side were beaten 4-0 at the Vitality Stadium.
The Cherries blew Chelsea away with four second-half goals as a Joshua King brace and efforts from David Brooks and Charlie Daniels saw the Blues fall to their heaviest Premier League defeat in 23 years.
The manner of the defeat means that Chelsea drop out of the top four and below London rivals Arsenal by virtue of goals scored – with new signing Gonzalo Higuain drawing a blank on his league debut.
It was Sarri's decision to replace Higuain with Olivier Giroud after 65 minutes which led to the travelling Chelsea fans chanting "you don't know what you're doing".
The Italian, whose side have lost their last three away games in all competitions, asked his assistants to leave the away dressing room and arrived for his post-match press conference almost 75 minutes after the full-time whistle.
Despite the lengthy debrief, Sarri conceded he was at a loss as to how Chelsea were so roundly beaten.
"In that moment I wanted to talk with them (the players) alone, without anybody," he said when explaining why his backroom staff were asked to step out.
"I needed to understand because it is impossible to play in so different ways in the first half and the second half. I don't know exactly (why) I want to try again tomorrow.
"For me, it is very difficult to understand why because after what I saw in the first half I thought there was a possibility to sort the problem, we have 43 minutes to play but not with that kind of reaction. It is 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 is also difficult 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."
Sarri said he did not feel under pressure but was instead "frustrated" and offered an apology to supporters when he was asked about their reaction to Higuain being replaced.
"In this moment I feel frustrated," he added.
"Not pressure, I am frustrated because I didn't see the sign of my work so I am frustrated. We have only to say sorry to our fans because we can lose, of course, every match we can lose, but not in this way, we need to solve the problem and we need to understand where the problem is."
Bournemouth boss Eddie Howe was still enjoying the moment when asked where the result stands in his history as manager – but was pleased with how his players put Chelsea to the sword after the break.
"It is up there," he said of the result.
"I don't know quite where it ranks at the moment, just like to enjoy the brief feeling you get from winning. The first half was a real examination of us defensively and I think we stood up to that.
"The (half-time) message was 'if we don't have the ball, don't worry' we were never going to dominate the possession of the game. We scored some great goals in the transition and showed our quality.
"The clean sheet is something we had to improve and change, the whole team defended so well tonight and if you saw that you wouldn't think that is where we have struggled this season."
The emphatic nature of Bournemouth's win was all the more surprising given main striker and reported Chelsea target Callum Wilson was missing after undergoing minor knee surgery which Howe feels will sideline the England international for three weeks.