United currently sit second in the Premier League table and have reached the semi-finals of the FA Cup, but their playing style has been heavily criticised this season and they suffered an early exit from the Champions League in addition to sitting 16 points adrift of leaders Manchester City domestically.
Mourinho is understood to be planning a mass overhaul of his squad in an effort to bridge that gap to their local rivals, and The Express reports that he is hoping to bring in five new players while losing as many as 10.
Luke Shaw's future at the club looks to be over after he was hauled off at half time of Saturday's FA Cup win over Brighton & Hove Albion, with Mourinho once again publicly criticising the full-back after the game.
The pair have reportedly been involved in a training ground row, which is likely to see the England international head the list of players to leave Old Trafford this summer.
Mourinho is also reportedly willing to ship out the likes of Juan Mata, Ander Herrera, Chris Smalling, Phil Jones, Daley Blind and Matteo Darmian, while Marouane Fellaini and Zlatan Ibrahimovic are out of contract and Michael Carrick is retiring.
The sales will be used to fund new arrivals at Old Trafford, and Mourinho is thought to have drawn up a wishlist of five players which is headed by Real Madrid winger and long-term United target Gareth Bale.