The pair were friends for 12 years before falling out at Liverpool.
"Things began to change when we arrived at Liverpool and were so successful," Ayestaran told the Daily Mail. "In England the people around the game, even for myself, make you feel that you're bigger than you really are.
"Sometimes you don't take care of the values and principles that made you so successful. Maybe we didn't have as much detail in training. I wasn't able to convince him that we should go back to our principles and stick to them.
"There was a difference between the beliefs that were so rooted in myself, beliefs that we applied for many years and got us success. We were running away from them.
"We stopped being critical with ourselves and sometimes we went through the motions. That's the reason I wasn't happy."