Manchester United will need to invest "a few hundred million" in order to become a serious competitor for the Premier League title once again, according to Gary Neville.
Sunday's 2-0 defeat at West Ham United has left United in eighth position in the Premier League table.
The Red Devils ended the clash in London with Jesse Lingard at centre-forward after Marcus Rashford was forced off the field with a groin problem.
Anthony Martial was also absent through injury while 17-year-old Mason Greenwood was unavailable for selection at the London Stadium due to an illness.
Neville has insisted that his former club have to back head coach Ole Gunnar Solskjaer in the transfer market and not "back out" if they wish to return to former glories.
"Ole needs three or four transfer windows to get this squad up to a level where they can compete," Neville told Sky Sports News. "And he needs a few hundred million quid - you can't back out of that. The days when you could pinch someone in the transfer window have gone. This is not going to be easy."
Meanwhile, former United boss Jose Mourinho, who was sacked last December, has claimed that the club could struggle to finish in the top six in the Premier League this season.
