Spanish champions Barca have a clearly defined way of playing that has been honed and refined from Johan Cruyff's 'Dream Team' days up to Pep Guardiola's current side, and Real have yet to find an adequate response.
Barca's domination of possession, intricate passing moves and suffocating pressure in Monday's game smothered the life out of Mourinho's expensively-assembled visitors, whose attempts to play on the break came to naught.
Real had come into the game unbeaten this season with a one-point lead at the top of La Liga, and had comfortably qualified for the last 16 of the Champions League and King's Cup.
"Barcelona played a great game," former Spain and current Cameroon coach Javier Clemente said.
"Real did not do the fundamental thing. If you let Barca have the ball they will destroy you."
Mourinho shrugged off the defeat, saying Barca were the 'finished article' whereas his team were still under construction, but that still leaves him with the problem of how to play against his former club.
Former Barca and Real coach Radomir Antic said: "The position of Real Madrid on the pitch was different to usual, even though he had the same players.
"Angel Di Maria and Cristiano Ronaldo had swapped wings and this, along with the changes (Lassana Diarra came on for Mesut Ozil at half-time), were more to hold than to go for the game."
Real had struggled in some away matches this year when they had not had the ball, but had usually come through because of the quality of their individuals, and this was an area they needed to improve, Antic added.
"Sometimes their play is rushed... they have yet to define their style. Monday's game is one to draw conclusions from, and perhaps they need to reflect on this."
The match build-up had predicted that the first 'Clasico' of the Mourinho era would be the closest in recent years.
Mourinho's stock could not have been higher in the local media. The man who knocked Barca out of the Champions League semi-finals on his way to winning the European Cup with Inter Milan last May, was expected to deal a major blow to their arch-rivals.
Luis Martin, a journalist for daily El Pais who knew Mourinho during his time working at Barcelona under Bobby Robson and Louis van Gaal, said the defeat would be a lesson for the Portuguese.
"He came with an aura of immortality," Martin told Reuters. "This result makes Mourinho more human, brings him back down to earth.
"His team's a work in progress. He's a person who doesn't like to lose but these types of defeats teach you a lot."
Get the best features, fun and footballing frolics straight to your inbox every week.
Thank you for signing up to Four Four Two. You will receive a verification email shortly.
There was a problem. Please refresh the page and try again.