The club had been researching proposals that would see the stadium capacity increase by 13,000 seats, with the aim of improving the atmosphere and corporate facilities.

Mourinho has been critical of the atmosphere at Old Trafford but, despite his frustrations, strengthening the squad remains the biggest priority.

The Portuguese boss has spent around £300 million since his appointment in 2016, but there are still areas of the team he wants to upgrade. And according to the Sun, there are six players who lead United's shortlist.

With doubts over the long-term futures of Paul Pogba, Ander Herrera and Marouane Fellaini, plus Michael Carrick's forthcoming retirement, Mourinho has instructed his scouts to scour Europe for new midfield talent.

Nice's Jean Michael Seri is thought to be a £35m target, along with Lazio star Sergej Milinkovic-Savic and Napoli's deep-lying playmaker Jorginho.

Victor Wanyama and Toni Kroos are also on United's radar, but the paper suggests Willian "could be the most likely to make the move to Old Trafford."

The Brazilian, valued at around £40m, worked with Mourinho at Chelsea and reminded his old manager of his quality by scoring in Chelsea's recent 2-1 defeat in Manchester.