The 36-year-old spent 17 years at Old Trafford, making 676 appearances for the club and scoring over 100 goals, before retiring at the end of last season.
Speaking ahead of his Scholes' testimonial against Eric Cantona's New York Cosmos, Ferguson praised the midfielder, who is expected to take on a coaching role at the club.
"To my mind he will go down as one of the greatest players of all time for Manchester United," Ferguson told reporters.
"I was with Fabien Barthez on Wednesday having a chat and he said 'pass my regards on to Scholesy, he's the best player I ever played with.'
"You see Xavi talking about Scholes, and he's in a better position than most of us to talk about midfield players, saying he's the best player he has ever played against."
United are scheduled to open their season on Sunday against Manchester City in the Community Shield.