Extra-time was beckoning when Sarri tried to substitute Kepa, but the goalkeeper dismissed the Chelsea boss' instructions and refused to come off.
Mayhem ensued, and ultimately Sarri did not bring Caballero on despite showing clear intent to, and his frustration almost boiled over as the Italian briefly left the pitch before coming back to the sideline.
Asked why Sarri wanted to replace Kepa, he said: "I was not on the other side, so I don't know".
The Spaniard eventually stayed on to keep goal in the penalty shootout, saving from Leroy Sane but allowing Sergio Aguero's effort to squeeze through his hands as City won 4-3 on spot kicks after 120 goalless minutes. "Kepa was right, but in the wrong way he conducted himself". "But it was not cramp and could go to the penalties". "I have talked to him [Kepa] but only to clarify because now I have understand the situation".
The Brazilian centre-back told Sky Sports News: "I just said to him we have to respect the decision of the coach".
When asked why he took a long walk down the tunnel before turning around and returning to the pitch, Sarri said, "I needed only to return to be quiet".
Shamima Begum: I am willing to change to keep British citizenship
Still upset, Rebecca said: "Of course, for the first hour when this story broke I felt furious and didn't like what she said". We were pleased to learn from your comments in the Commons that you recognise my nephew, Shamima's son, as a British citizen.
"I think the coach he wished to do the substitution because [he was not sure] of the injury, he didn't understand that".
"This was nothing to do with the problems I had this week, with [hamstring] it wasn't that".
'I feel the image that has been portrayed was not my intention.
When about his future, the Italian added: "You have to ask the club". I can only answer with my opinion. Here I am very happy and in the last three matches we are improving and have improved a lot. We were close to winning, obviously we're sad that we didn't, and I think the team needs to continue playing like this, because today we've shown we can compete against the best teams. I am happy with my players.
Sarri came into the match under intense pressure following a disappointing run of results and the Kepa incident led to further questioning from the media.