Neville says United cannot risk another window of panic buying.
He told Sky Sports: "In the last five transfer windows they have spent some money. In the previous ones to that, maybe there was under-investment because Sir Alex was happy with the squad that he had.
"I like to go back and look at things. We were sat here 12 months ago and as a Manchester United fan if you'd said to me the champions of England, who'd just beaten Swansea away from home, were going to spend £140million in the next 12 months and be where they are today I'd say you're mad.
"Of course they need to spend because they have to; they have to bring more players in. There's no doubt about that. But it's critical they bring the right players in.
"They've spent £140million in the last 12 months and they've got Zaha, Herrera, Shaw, Fellaini and Mata. Last season I'd argue that some of those buys were panic buys, who didn't fit the philosophy - and they're paying for it now."
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