Betis had the lead through Ez Abde, before Chelsea stormed back to win through goals from Enzo Fernandez, Nicolas Jackson, Jadon Sancho and Moises Caicedo all after halftime.
And for Cole, it was Palmer who inspired the fight-back. He said on TNT: "Cole Palmer is an absolute genius.
"We don't produce these players. They don't fall off trees.
"He took the game by the scruff of the neck and there are not many players in world football that can do what he does."
Chelsea manager Enzo Maresca also said afterwards: "The bad moment, the bad run he had during this season is going to make him a better player, no doubt.
"We all know he's a top player. We need to help him to be in the right position, the right moment.
"He is a quality player. In the last third, he can decide a game with a goal or assist."