The Mali international revealed he turned down the chance to join los Blancos before entering into an agreement with the Blaugrana and spoke of his admiration for Pep Guardiola
The 34-year-old spent four years in Catalunya, winning La Liga three times and the Champions League twice, as well as many other accolades.
Since then Keita has played in China for Dalian Aerbin and revealed earlier this month that he was in advanced negotiations with Liverpool before joining Valencia, but says his decision to sign for the Blaugrana in 2008 instead of Madrid's proposal was vindicated.
"One day, in Almeria, before signing with Barcelona, I had an offer from Real Madrid," he told El Diario.
"But I called my agent and said, 'go to Barcelona!' And he asked why. My response was: 'I do not know, but we are going there.' And I was not wrong."
Keita also revealed his admiration for Pep Guardiola, who he played under at Camp Nou, and cited the coach's empathy for former Barca defender Eric Abidal in his time of need as an example of his managerial skills.
"Pep is a fantastic person If you need anything, he'll give you it all," Keita continued.
"I remember Abidal had a problem in his family and he approached him one day and said: 'Go and when you are all well, come back'.
"When a coach tells you that, you come back, play and give 200 per cent. If the player is happy, you get so much more out of him and Guardiola recognised this.
"He was also amazing as a coach, treats all the players the same and gives everybody confidence. Tactically, he's very good."