The French playmaker gave a mature and, at times, magical display against the Black Cats, topping his day off with an outrageous Rabona cross for Phil Foden to put the game to bed.
The 22 year-old then left to a standing ovation - and a warm hug from his manager.
“Rayan is an exceptional player,” said Pep.
“He is so young, proved his personality at Fulham. Every time he had the ball he gave us extra passes and in the final third he has something special.
“What I admire the most with Rayan is not the skills. I never saw Messi play this cross and he is the best player.
“I never saw him do this, if the cross is fine it’s fine. Whether with your right, left, if it’s effective, it’s fine. I learned from Messi that I never make a mistake with the simple things.
“Simple things, he does perfectly. I want my players to do the simple things well. After that, if you have special talent that your mum and dad give to you you can do whatever you want - but if he doesn’t work then we have a problem.“
Watch Pep’s full post-match press conference by playing the video above...
