Maurizio Sarri gave Kepa Arrizabalaga a rollicking in the Wembley dressing room after the Carabao Cup final.
Kepa, who twice required treatment in extra-time, waved away a substitution before Manchester City won the penalty shootout and lifted the trophy.
Chelsea manager Sarri insisted it was a misunderstanding, but privately the Italian was furious with Kepa for disobeying his orders and blasted the keeper for his actions.
A furious Sarri shouted: “How could you do this?”
Chelsea defender Antonio Rudiger attempted to diffuse the situation between the pair, having been seen talking to his irate boss on the pitch before the shootout.
Kepa has been fined one week’s wages and admitted he made a “big mistake” after refusing to be substituted.
He admitted he had handled the situation poorly and apologised after remaining on the field when Sarri was attempting to send on Willy Caballero as a replacement.
“I have thought a lot more about yesterday’s events,” said Kepa, who broke the transfer record for a goalkeeper when he joined the Blues in August.
“Although there was a misunderstanding, on reflection, I made a big mistake with how I handled the situation.
“I wanted to take the time today to apologise fully and in person to the coach, to Willy, my team-mates and to the club. I have done this and now I want to offer the same apology to the fans.
“I will learn from this episode and will accept any punishment or discipline the club decides is appropriate.”
Sarri said: “Kepa and I have spoken about the incident. It was a good conversation.