Manchester United have added Pau Torres to their list of defensive targets.
Ole Gunnar Solskjaer will consider signing a defender in January if his back-four continue to falter.
ESPN says the Norwegian has been impressed by Villarreal stopper Torres, as well as Sevilla enforcer Jules Kounde.
United first need to sell Phil Jones and Marcos Rojo before moving for another defender.
Some space has been freed up after Chris Smalling was sold to Roma at the end of the transfer window.
However, Eric Bailly and Axel Tuanzebe will also be given a chance to stake their claim after Harry Maguire and Victor Lindelof's poor start to the season.