He revealed that he considered signing Raul - the all-time record goalscorer for Real Madrid - when the 33-year-old left Spain last summer.
Instead, Raul - the top all-time marksman in the Champions League with 71 goals - joined German club Schalke and has led them to a semi-final showdown with United.
Ferguson said: "Raul's agent spoke to us when his time at Real had come to an end and I was a bit tempted because you say to yourself: he's not too old to score a goal in the Premier League.
"He had a fantastic career at Madrid and players like that always find something in terms of ambition. They don't just wither away. He still had plenty to do. But we had Michael Owen as an experienced player, as well as Dimitar Berbatov and Wayne Rooney plus we had signed Javier Hernandez.
"If I hadn't got Michael Owen I might have been tempted.
"Raul's got a fantastic goal record - 71 goals in the Champions League is an incredible record. I hope it stays at 71 for the next two weeks!
"You've always got to be careful with him in the last third because he's still got intelligence and all that experience."