City's Football Development Executive is forecasting a tough few years for the Red Devils, and says if City win the Premier League it would be a huge psychological blow to United
Scholes announced his retirement from the game following United’s title-winning season last year.
However, the former England man made a dramatic U-turn earlier this year, and was named as a substitute for their 3-2 FA Cup win over City in January.
But while Vieira is full of praise for the midfield maestro, he thinks the 37-year-old's return shows that Sir Alex Ferguson's squad is lacking in depth and says they could be in for a tough few years following the sale of Ravel Morison and potentially Paul Pogba.
“Paul Scholes is a player that I really love and admire, one of the best English players of the last few years, and seeing him come back is good for him and for United,” he told reporters.
“But for him to come back just shows a little bit of weakness in United, because they had to bring a player back who was 37.
“I think it shows that, in the next few years, it will be really difficult for United to cope with other teams because, with all the respect I have for Scholes, him coming back shows that they don’t have talent in there to replace him.
“When you see United losing young players like Ravel Morrison and maybe Paul Pogba, they should be really worried because that wouldn’t have happened in the past.”
Vieira’s side take on Chelsea on Wednesday night as they look to close the gap on their neighbours to just a point.
City are looking to win their first league title since 1968, and Vieira believes if the champions lose the crown to their city rivals it will prove a lot harder to bear than in seasons gone by.
He continued: “When United lost [the title] to Arsenal, they were in Manchester and Arsenal were in London, so it is different.
“It will hurt United a lot more to lose the title to City.”
While City have begun to feel the heat in recent weeks, dropping out of the Europa League and losing at Swansea, teams around them like Arsenal have been going from strength to strength.
Yet Vieira says they are happy with the position they are in and claims the pressure is part and parcel of fighting for titles.
“Arsenal and Chelsea, they all want to be in our position, so it is something we have to enjoy,” he added.
“You want to feel the pressure when it is a positive pressure. You would rather feel that pressure than the one that comes with being at the bottom.”