"I don't think United can have a transitional period," Atkinson told MUTV. "You don't hear of Barcelona or Real Madrid having transitional periods.
"What David probably means is that there has to be an evolution. They need two or three new players. They are not good enough in certain areas.
"It might take a little bit longer than he thought for those types of players to come in, but I don't think you can have a transitional period at Manchester United."
United currently lie in ninth place in the Premier League table.