are concerned that is struggling to settle at the club and fear a repeat of the Angel Di Maria fiasco.
Sanchez became the highest-paid player in the on a total of £600,000 a week when United gazumped rivals Manchester City to sign him from Arsenal in January.
However, the 29-year-old's disappointing form has produced only one goal in 10 games and he was on the bench for the first time when 's side beat Brighton in the FA Cup last Saturday.
Sanchez, who is preparing with the Chile squad for their internationals against Sweden and Denmark, has a reputation for being single-minded and sullen at times.
However, staff have been surprised by his miserable demeanour at the club's Carrington training ground where he cuts an unhappy, isolated figure and often eats alone in the canteen.
Some say he comes across as a player who is having second thoughts over his decision to join United in a swap deal for Henrikh Mkhitaryan.
They have drawn comparisons with Di Maria, who was a British record signing when he moved to Old Trafford for £59.7million in 2014 but joined Paris Saint-Germain in a £44m deal following a dismal season in England.
-Dailymail