Calderon, who was in charge at the Santiago Bernabeu from 2006 until 2009, added that several players in Los Blancos' squad are unhappy.
As well as not speaking to the Brazilian playmaker, it has also been reported that former Borussia Dortmund star Nuri Sahin also has a difficult relationship with the Portuguese boss. Both Kaka and Sahin are struggling to make the starting lineup at the Bernabeu, with rumours circulating that transfers out of the club are likely.
"The players are no longer happy. He [Mourinho] hasn't spoken to Kaka once in the last four months," Calderon said to Ona FM.
"The Spanish players are unhappy with their situation because of the privileges Mourinho gives to the Portuguese players.
"And then there's the situation of Sahin. The reason he doesn't play is because Mourinho doesn't like him."
Real Madrid face Athletic Bilbao at home in their next league match tonight.