The Barcelona defender believes his old boss made a mistake in allowing him to leave the club but remains grateful for his time at Old Trafford
The Spanish centre-back made his way through the Blaugrana's famed academy as a youth player but signed his first professional contract with the Red Devils in 2004, only to return to his childhood club four years later.
And now the 26-year-old, who has gone on to win a score of honours with the Catalans, has revealed that he enjoys letting his former boss know how wrong he was to sell him, but believes his time in England made him a better player.
"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!" the defender told The Daily 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."