There were extraordinary scenes in the 2019 Carabao Cup final between Chelsea and Manchester City exactly two years ago.
He was fine to continue but Maurizio Sarri decided it wasn't worth the risk and wanted to replace him with Willy Caballero.
The Argentine was ready to come on and the fourth official signalled for Kepa to make his way off the pitch.
However, he wasn't having any of it.
The Spanish goalkeeper decided he was going to call the shots and he refused to leave the field.
Maurizio Sarri, understandably, was absolutely fuming.
He couldn't do anything about it though and Kepa eventually won the battle.
Watch the moment below:
The whole episode really was extraordinary.
Unfortunately, Kepa wasn't able to guide Chelsea to victory in the shootout.
He managed to save Leroy Sane's spot-kick but failed penalties from Jorginho and David Luiz saw Chelsea sink to defeat.
Maurizio Sarri calmed down by the time he conducted his post-match interviews.
"I misunderstood the problem and only realised the situation when the doctor arrived at the bench," he said.
"He understood I asked for a change for his physical problem. He said: 'I haven't a physical problem.' And he was right.
"I realised after, when the doctor arrived. I have talked to him [Moss] but only to clarify because now I have understood the situation.
"It was a big misunderstanding because I understood the keeper had cramp and was unable to go to penalties. But it was not cramp and he could go to the penalties.
"I needed to return [down the tunnel] to be quiet."
Kepa also believed it was a misunderstanding.
"It was misunderstood. In no moment was it my intention to disobey or anything like that with the boss," he said.
"It was two or three minutes of confusion until the medics got to the bench and they explained everything well.
"He thought I couldn't continue, and - fundamentally - I was trying to say that physically I was fine."