In an exclusive interview for a special Sir Alex tribute magazine created by United Review, the Treble winner says he will always be grateful to the manager for guidance and encouragement during his trophy-laden time at Old Trafford.
"The boss deserves almost all the credit [for how my career has turned out]," Beckham told us.
"It’s 50/50 with my parents – that’s how highly I regard the boss. My parents were the ones that brought me up and helped get me to a certain level in my career, and the manager is the one that took me to a whole different level of playing for Manchester United and for England.
"He was the one that gave me my chance as a young kid. He gave me my debut at Brighton [in September 1992] and my Champions League debut against Galatasaray when I played at Old Trafford and scored my first goal for the club.
"He’s the sole reason why I was successful at Manchester United and successful in my career.
"You see so many young players fall by the wayside but under the boss that was never going to happen. He looked after us all and gave us everything we needed to become the players and the men that we are today."
As Sir Alex prepares to celebrate 25 years at the Old Trafford helm on Sunday, Beckham insists his former boss is quite simply a one-off.
"It [spending 25 years at a club like United] just doesn’t happen in football anymore. That loyalty and respect for just one club is unbelievable and it’s not something you see these days," explained the midfielder.