The Paris Saint-Germain boss has revealed the role that the Portuguese played at Camp Nou when he was Bobby Robson’s assistant.
The current Chelsea boss started out as a translator at the Catalan club before making strides in the management world and was with the Blaugrana at the same time as the retired French defender in 1996-97.
Blanc stated that the Barcelona players realised at the time that Mourinho was an intelligent man and had all the traits necessary to be a successful coach.
"Mourinho has a fantastic history at Barca,” the now Paris Saint-Germain boss told BeIN Sports, published by Spanish newspaper Sport.
“Bobby Robson did not speak Spanish and Mourinho was there mainly to make his life and communication easier. He speaks three, four or five languages. It was to facilitate the acclimatisation of Robson.
"After a month, the method of training was different and the players wanted to change. Robson put Mourinho in front of the players because he knew how to speak to them..
"I think in this moment, it all began. We saw he was very intelligent and wanted to do it. Louis van Gaal arrived and he had the intelligence to stay and learn from him. The rest is history.”
Blanc only spent a solitary season at Barcelona with Mourinho before moving on to sign for Marseille.
Mourinho has gone on to become one of the game’s most distinguished and successful coaches, winning the Champions League with Porto and Inter and domestic titles at Real Madrid and Chelsea.
The at-times outspoken Portuguese trainer has led his Blues side to the top of the Premier League, with a 5-0 victory over Swansea last weekend giving the Stamford Bridge outfit a five-point lead at the table’s summit.
Mourinho and Chelsea will face Blanc and PSG in the Champions League last 16 next month.