But nine months on and United's decision to make Sánchez the best paid in Premier League history has been questioned. The 29-year-old has struggled for form at Old Trafford and has scored just four goals in 25 appearances.
And with Anthony Martial and Marcus Rashford waiting in the wings, should Sánchez still be a regular starter for the Red Devils?
But should Mourinho think the same? We dived into the data to find out what's gone wrong for Sánchez at Old Trafford and whether it's time for him to be taken out of the starting XI for a prolonged period.