Manchester United are considering letting Chris Smalling and Phil Jones leave as they plan to bring Raphael Varane and Harry Maguire.
United boss Mourinho is looking to bring in a new centre-half, with Smalling set to make way and fellow England defender Jones also under serious threat.
Mourinho is understood to have had misgivings about the pair even before Sunday’s shambolic 1-0 defeat at Newcastle.
His loss to the bottom half placed side dragged his second-placed team backwards into a battle with Liverpool, Tottenham and Chelsea over finishing in the top four.
The defeat underlined his vulnerability in the back at St. James’ Park and the manager is set to overhaul everything.
Mourinho saw rivals Liverpool and City splash out £75million and £57m respectively on centre-backs Virgil van Djik and Aymeric Laporte last month, and has told United chiefs they must start spending big on defenders, too.