The centre-back left Barca in 2004 in favour of signing a professional deal at Old Trafford.
However, Ferguson opted to sell the Spanish international back to his boyhood club and he has since gone on to win numerous trophies with the Catalan outfit, including two Champions League titles at the expense of United.
Despite insisting that Ferguson was "wrong" to allow him to leave, Pique has admitted that he looks back on his time at United with fondness.
"I am proud to have been part of a Sir Alex Ferguson team. Even though every time I meet him I tell him that he got it wrong with me." he told The Telegraph. "The kid who went to Manchester was a boy of 17 who found himself in a changing room full of stars and had a wonderful time [remains]. I remember when I was called to train with the first team, it was wonderful.
"That prepared me for what was coming, for the return to Barcelona. Without that pressure, I would have been a bit green when I came here.
"I am very proud of my three years there, of having decided to go to Manchester first. At 17 it was the perfect time for me to leave home because it helped make me as a person."
Pique made a total of 23 appearances for the Red Devils.