Speaking on Movistar Plus, Valdano — who resigned as Madrid's director general in May 2011 following a year of tensions with Mourinho — assessed both the immediate opportunity and the longer-term risk of the appointment.
"Mourinho, I think, will arrive with his most seductive face. At the beginning everything will be very calm, I think the players will also respond because there is no Club World Cup in the way. I suppose the pre-season will be a little more demanding and that will help improve the squad's performance."
His analysis of what the squad needs was direct. With Florentino Pérez committed to keeping the club's star players, Valdano identified the defensive positions as the most urgent area of need.
"Within Florentino Pérez's project, which considers football as a business of heroes, he is not going to sell the heroes. That is certain."
He continued: "At least four defenders are needed, and a midfielder who gives balance to the squad."
That structural arithmetic, combined with Pérez's reluctance to move established names, creates a complex transfer puzzle for any incoming manager to navigate.
Valdano also offered a sobering warning about what happens once results begin to go against Mourinho, drawing on personal experience of the first spell from 2010 to 2013.
"Let's see what happens as time passes and when the defeats arrive. Whether peace will be possible or whether we will continue with this somewhat turbulent situation we have lived through this season."
He was also careful to frame the challenge as collective rather than managerial.
"This isn't something Mourinho fixes alone."
Mourinho has agreed a three-year contract in principle with Real Madrid, according to some sources, and is expected to be formally announced after Benfica concluded their domestic season at the weekend.