The Blancos legend believes the Portuguese held the most authority as a coach at Santiago Bernabeu in the last 20 years
The Portuguese coach endured a turbulent relationship with his squad in his final season in the Spanish capital, culminating in a high-profile falling-out with club captain Iker Casillas, and former defender Hierro suggests the 50-year-old's sway at Santiago Bernabeu may have contributed to such disputes.
"Every club is different and Madrid is even more so," the 45-year-old told Fifa.com.
"Madrid is a club where you have to win and it’s a place that can wear you down – where people have a different way of thinking.
"If you were to ask me to look at the last 20 years in Madrid’s history and say which coach has had the most decision-making power at the club, I’d say there’s no doubt he [Mourinho] is the one.
"If you ask him though, perhaps he’d say he didn’t have as much authority as he’d have liked. But everyone knows him perfectly."