Erik ten Hag only wants to keep one of Eric Bailly, Phil Jones or Axel Tuanzebe this season after signing Lisandro Martinez from Ajax.
The 24-year-old completed his £47m move to Old Trafford today, becoming the Red Devils' third signing of the summer after Tyrell Malacia and Christian Eriksen.
Martinez bolsters the Ten Hag's defensive options, with the Dutchman expected to pick two starters from the Argentine, Harry Maguire, Victor Lindelof and Raphael Varane.
United will need strength in depth this term given their involvement in the Europa League and the unique timing of the World Cup,
meaning the Ten Hag wants another player to back up the quartet.
He has an open mind as to who it is, but there is only one vacancy.
The two Jones, Tuanzebe and Bailly will be sold, with the trio now fighting for their futures at the Theater of Dreams.
Bailly has attracted the attention of Roma and Jose Mourinho would love to be reunited with the defender.
The Ivorian defender was Mourinho's first signing at Old Trafford in 2016 when he joined from Villarreal for £30m.