The 18-year-old left-back is said to be the Red Devils’ top target ahead of the summer transfer window on the back of his impressive breakthrough with the Saints.
Despite his age, Shaw is already a first-team regular on the South Coast and is even being tipped to make England’s World Cup squad following his recent senior international debut.
United are rumoured to be willing to gazump all other interested parties to land the teenager in the coming months with a £30m offer, but now the player himself is said to have reservations about a potential move.
With United having sacked David Moyes last week, the identity of the man set to be in charge at Old Trafford is unclear.
Reports have suggested that Louis van Gaal will take the role, but as it stands nothing is clear.
Shaw wants to know who he will be playing under before committing to a switch and is seeking assurances that he will be a regular starter.
As well as United, Liverpool, Tottenham and Chelsea are said to be keen.