The former midfielder believes there will have to be a number of new faces at Old Trafford for a title challenge.
United have already completed the signing of highly rated Dutch youngster Memphis Depay from PSV after moving to secure him ahead of a number of their main rivals.
Manager Louis van Gaal is expected to radically overhaul his squad in the summer though, with a series of unwanted players likely to leave and several new faces expected to arrive at Old Trafford as the Dutch tactician looks to strengthen in most areas.
And Scholes suggests they need at least five signings to catch current champions Chelsea in the Premier League.
"I think United will be looking for three or four players,” he said.
“Maybe a centre-back, a right-back, possibly another goalkeeper, a top class centre-forward, and even maybe a wide player so that is five players.”
United started the season poorly this season but have rallied in the second half, although even that has been littered with disappointing displays, such as the recent run of three straight defeats.
However, they have performed well against their top four rivals in the big games, having beaten Manchester City comfortably, drawn against Arsenal recently and only narrowly lost to Chelsea, although they dominated all of the statistics throughout the game, and Scholes believes they are not too far away from a challenge.
"We have seen them in the big games against the big teams and they have not been far away,” he added.
"They have a way to make up with Chelsea and Manchester City. Arsenal don't worry me as much. But there is quite a gap between them top two and it's gap they will have to have to bridge."