Andrea Mancini, who is currently on the books at Spanish side Real Valladolid having been released by City this summer, believes his father is doing a good job at the Etihad Stadium despite his critics.
He said in Marca: "I don't understand the criticism. He's just become Premier League champion with City, which they haven't won for 44 years. I don't know what more he has to do."
Andrea Mancini was also asked about any similarities between Roberto and Mourinho, who come face-to-face in the Champions League on Wednesday night.
The 20-year-old said: "They aren't alike. My father was a player for many years and you notice this. He has a lot of experience and knows more about football than Mou.
"Mourinho is more psychological, more of a motivator, he knows how to manage the minds of the players. The ideal coach would be a mixture of the two."