Goals from Gonzalo Higuain and Jorginho brushed Fulham aside in a 2-1 west London derby win that leaves Chelsea five points off third-placed Spurs with a game in hand.
Sarri said: “With another man, yes, of course. I could have done it in another way. With him, I know him very well and know very well it wasn’t the right solution.
“It was a normal decision, I think.
“Kepa made a big mistake. He paid for it with the club and the team. Now the situation is closed.
“There was only one other way: to put him out of the squad for the rest of the season. But Kepa is a man and understood, and reacted very well today.
“I could have killed him, but I think that was right.
“I spoke with him during this week and he understood. His behaviour during the week was really very good.”