United sit some 34 points behind Liverpool in fifth, and are locked in a battle to secure Champions League football for next season.
"There is a big gap to close, there's no doubt about that," Scholes told BBC Radio Five Live.
"The points difference is ridiculous and the quality of Man City obviously is there for everyone to see.
"I really don't think they are a million miles away. I know we spoke about four or five players but I think it's two or three now.
"I think you are looking at a centre forward, a really classy goal scorer and possibly a centre-half to play next to [Harry] Maguire.
"Look, I think [Victor] Lindelof has done alright but I just think Maguire with his lack of pace at times (can get caught).