Not 24 until next month, Rooney's storming start to the current campaign has seen him pass a century of United goals and join the pacesetters in the race for the Barclays Premier League golden boot.
Having worked closely with the England international for half a decade, Sir Alex is in little doubt as to how far Rooney can go.
"He hasn't at any point disappointed us," the United manager said at his pre-Wolfsburg press conference. "When we signed him as a young kid we thought exactly the same as today; that he will become a real top player.
"There are some great players like Kaka, Ronaldo and Lionel Messi - they're the three best players in the world, I think, and Wayne could easily get to that level, with the right progress.
"He is going in that direction without question. He's blessed with certain ingredients that only great footballers have. Great determination and hunger to win every match. Every time he goes on the field, every training session, he's blessed with that. It won't ever change for him and these are wonderful things to take into the game of football today.
"You sometimes wonder about the criticism of what footballers get paid, but when you see that effort he puts in, he's worth every penny he's paid. He plays as if he means it and I think it's a wonderful thing to have."
Sir Alex brackets Rooney alongside a number of United greats who have given their all for the cause, and he points out that the striker's