However, the former Bayern Munich midfielder was plagued by knee injuries and restricted to a mere five appearances in the three seasons that followed.
Fergie was particularly brutal about the former England international in his 2013 autobiography, calling Hargreaves "one of the most disappointing signings of my career" and "too nice" to make it to the top.
"When I signed him, there was something about him I didn't like," Ferguson wrote in his book.
"He had no confidence in himself whatsoever. He didn't show nearly enough determination to overcome his physical difficulties, for my liking.
"I saw him opt out for the easy choice too often in terms of training. He was one of the most disappointing signings of my career."
Taken aback by what he read, Hargreaves sought about discussing the comments over the phone.
"I rang him, when I heard. I was surprised myself. My family were really surprised," Hargreaves told the Manchester Evening News.
"I think anyone who's been around me knows that I left home at 15 alone, to go to a country where I couldn't speak the language to play football.
"I left the comfort of Bayern Munich to play for Man United because I wanted to represent Man United, to play for Sir Alex and be part of that great team. I never took the easy step. I played for a country I wasn't even born in because I wanted to be the best.
"I probably never should have been a professional football player, based on my start! But I worked my way and, obviously, didn't finish the way I wanted. A lot of things went into that."
While Hargreaves acknowledged Ferguson had good reason to be disappointed with how the move panned out - he told the Scot it pales in comparison to the regrets he has over his career.
Hargreaves continued: "As much as it was disappointing for him not having me play - because when I was fit, he played me all the time. I told him on the phone, I promised him, it broke me more than it did him. Because that was my career.
"To this day, I haven't done a day of sport since. I can't because of my knee. If you just forget the football side, my career changed from one day to the next and for a young man chasing a ball around all of his life, it was a pretty significant day.
"I haven't been able to play sport like that since. To say it went the way I envisioned would be a lie."
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