Scholes is also critical of Antonio Valencia at right-back.
He told the Manchester Evening News: “Blind is a better defensive midfielder for United than he is a centre-back but he's been an excellent partner for Eric Bailly so far this season, hence why Chris Smalling is not in the team at the moment yet he's not won everybody over yet.
“Why? Because he's physically limited in the Premier League and people are expecting him to be found at some point, I suppose I still am, and against City he was found wanting against a dynamic Kevin de Bruyne.
“I would rather see Smalling partner Bailly in the long-term."
The former Old Trafford midfielder then turned his attention to Valencia.
“As for Valencia, he's not a right-back. He never will be, regardless of how good his form is at any one time," added Scholes. “But Matteo Darmian hasn't got a sniff yet and there are different questions to ask about whether Timothy Fosu-Mensah is ready to start right there, so it's a more difficult situation."