Thomas Tuchel backed a Chelsea fan who was involved in an altercation with Cesar Azpilicueta after the final whistle of defeat to Arsenal.
Chelsea captain approached the supporter following the 4-2 loss and appeared to be involved in a heated exchange.
Tuchel, who was furious with his players after a third straight home defeat in all competitions, refused to criticise the fan.
He said: “I was not part of it. I saw it, but honestly, I can understand the fan.”
Chelsea’s manager could not hide his own frustration after seeing his team make it 11 goals conceded in their last three matches at Stamford Bridge, in an error-strewn display.
He said: “It’s a level of mistakes, the number of mistakes in consecutive games here at home. It’s impossible at this kind of level. You don’t see this. It’s simply impossible - but we’re doing this at the moment and you cannot win football games like this.
“They get full praise when they do it, when they did it for the last three matches. And they have to face the reality that it’s impossible to win matches if you make this amount of mistakes of this calibre. It’s simply impossible.
“I don’t see it in any other matches, but I see it now in consecutive matches of our games and it has to stop.”
Andreas Christensen’s under-hit back-pass gifted Eddie Nketiah an opening goal after 13 minutes.
Malang Sarr and N’Golo Kante were then involved in a mix-up in the second half that saw Nketiah pounce again to make it 3-2.
And Azpilicueta was guilty of needlessly bringing down Bukayo Saka in the box late on, from which the Arsenal striker scored from the spot.
Tuchel added: “Look at the penalty. It is an unbelievable goal from our ball possession. There’s no tactics behind that. We have three ball losses in 10 seconds. Then we do a foul where there’s not even the slightest danger.
“We foul a person. It is a penalty and we rob ourselves of the chance to have six minutes for an equaliser. What is there to analyse? There’s nothing to analyse.
“How can you do three, two, one big mistakes in matches? How can you? You cannot?”
