The Red Devils have already spent a combined £56m on Athletic Bilbao midfielder Ander Herrera and England international Luke Shaw in the summer transfer window.
To be able to compete with the likes of City, Liverpool and Chelsea – who you’ve seen are spending a lot of money as well – you have to splash the cash
Van Gaal is set to take charge of United following the Netherlands’s World Cup campaign after agreeing a three-year deal with United in May.
And former Red Devils striker Yorke feels the Dutchman needs another four or five top signings if Van Gaal is to have a chance of breaking the top four.
Yorke told Sky Sports News: “We know there are six or seven players that they’re trying to buy and we are seeing the aggressiveness of Manchester United splashing the cash.
“And they need to. Last season was a bit of a disaster for Manchester United from that point of view and I don’t think they can afford to be left behind like they have done,
“They did not qualify for the Champions League and were not even being on the front of competing for the Premier League.
“That was a huge blow and to be able to compete with the likes of City, Liverpool and Chelsea – who you’ve seen are spending a lot of money as well – you have to splash the cash.
“That’s certainly what Manchester United are trying to do at this time.”
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