Fabregas established himself in Arsenal first team as Mourinho was winning his first of three Premier League titles at Stamford Bridge at the end of the 2004-05 season.
Arsenal and Fabregas were regularly left in the shadow of Mourinho's Chelsea before the midfielder returned to Barcelona and had to watch the Portuguese win La Liga in his first season back in Spain.
However just two years later and Fabregas was lured back to England by Mourinho to join Chelsea and this time was part of a title-winning team.
"He was my enemy when he was in charge at Madrid or Chelsea, competing and wanting to beat him," Fabregas told Vanity Fair of Mourinho.
"From there I became his player at Chelsea and would go with him to death. I learned a lot, I have a very positive memory of him. Forever."
Fabregas' future at Stamford Bridge was in doubt over the summer, having started just 13 league games last season.
However, after rejecting a move to big-spending AC Milan, Fabregas is now enjoying a more prominent role under Antonio Conte.
"I have found absolute happiness at Chelsea," he said. "The family is delighted, totally adapted to life in London and the fans love me.
"I am too happy to change clubs, I just miss my family and my friends in Barcelona."