For the season opener, United will be without quite a few first-team regulars owing to injuries and match fitness.
"At United we have to sign big players, with experience", Sanchez told Sky Sports.
Mourinho's squad should be boosted by the return of World Cup victor Paul Pogba, who arrived back at Carrington on Monday, and Anthony Martial, who did not travel to Munich for the friendly against Bayern after leaving the US tour and missing more than a week of training to attend the birth of his son in Paris.
Timothy Fosu-Mensah set to join Fulham on loan
Since then he has made a further 11 appearances for the Red Devils and his current contract takes him to 2020. Fulham boss Slavisa Jokanovic has been involved in a busy transfer period for the newly-promoted club.
At 5pm Premier League clubs will no longer be allowed to bid for new players either on loan or in a permanent deal until the winter transfer window begins on 1 January 2019.
United purchased Fred from Shakhtar Donetsk for a fee of around £54 million with the hope that he would be able to solve their problems in midfield. United said they were happy to be kept informed. New-signing Fred is also expected to start for the hosts today. "United finished above them last season", said Scholes, speaking in Hong Kong. Matteo Darmian may yet be sold with great interest in him from the leading clubs in Italy although none of them have got close yet to United's asking price. "I'd prefer to have them even if they are not top, top, top (in terms of fitness)".
Asked at a news conference on Thursday whether he had the squad to go head-to-head with Manchester City for the title, Mourinho refused to answer one way or the other.
To be fair to Sanchez, the season is only young, but he does have previous with this sort of thing, as his performance away to Crystal Palace last season (he gave the ball away 19 times) suggests.
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"It was my first goal and that is all that was important, it doesn't matter how I scored", he said.
"In football you need time to work and players on the pitch to work and we didn't have until now".
"I think Manchester United are a little bit desperate at this present moment which is not like Manchester United and certainly not like Mourinho".
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