In order to close the gap to Liverpool and Manchester City and compete for the Premier League title, Manchester United need to make five signings in the summer transfer window, according to Gary Neville.
The Red Devils are poised to complete a deal for Ajax midfielder Donny van de Beek, but that would be the first signing they have completed since the season finished, while the likes of rivals Chelsea have spent £136m.
Last season, United finished a huge 33 points behind eventual champions, Liverpool, and if they are to close that gap this season, they must step up their recruitment, particularly of a 'world class' centre-back, says Neville.
"The Manchester United squad, as it stands today, cannot challenge for the Premier League title this season," the former United defender told Sky Sports.
"The squad needed four or five improvements and it still needs four or five improvements. I've been saying that for a year and I've even nominated the positions I feel they need to improve.
"They have to sign a world-class centre-back. For me, another midfield player. I also think a right-winger, a centre-forward and you have to look at left-back because of Luke Shaw's injuries and the fact he has obviously been in and out of the team in the last two or three years.
"So, I think there are definitely four or five players required and to not get three I think it would be a problem because of what the other clubs are doing. If Liverpool get Thiago, if Manchester City do what they are looking like they are going to do and with Chelsea doing what they've done, they are your competitors and they all look like they are improving and moving forward.
Neville does believe that Man Utd's transfer strategy has improved in recent years, though, and hopes former team-mate Solkskjaer can be aided by the board to get new signings sealed quickly.
"So, United have to do business but I do believe more in the strategy of what's happening, they just have to get the deals over the line," he continued.
"That's not always easy but they have to try and do it quickly to give Ole the time to build to get this team moulded for the start of the season."
As well as Chelsea spending big this summer, Man City have signed Nathan Ake and Ferran Torres and continue to be strongly linked with one Lionel Messi, while Liverpool are still looking to sign Champions League winner, Thiago.