Pique has formed an impressive defensive partnership with Barca captain Carles Puyol at both club at international level, winning nine trophies since signing for the Catalans in 2008 and the World Cup with Spain last summer.
He has also been described by Germany legend Franz Beckenbauer as the best defender in the world, but Pique claims he might not have been able to hit those heights had he stayed at United.
Ready for action: Barcelona's Gerard Pique comes up against his old team tonight
'When I left, maybe it was the best decision for Ferguson, for me, for Manchester United and for Barcelona,' he said.
Pique found his passage to the first team blocked at Old Trafford by the fine form of Nemanja Vidic and Rio Ferdinand.
'After that, when I arrived here, I was really lucky to have a lot of minutes to show that I can play, that I can do it well,' he said. 'Maybe Sir Alex (Ferguson) would want me to be there again but football is about decisions and he took that decision.'
Pique started just 12 league games in three seasons for United and his only regret is that lack of playing time.
Struggles: Pique failed to hand down a regular starting spot during his brief stint at United
He continued: 'I had three really good years in Manchester, but maybe I could have played more. But I wanted to leave, because Barcelona was my home and since I was a child I have been a fan of Barcelona - so I wanted to go there. Ferguson understood me and our relationship is good.'
However, Pique retains much respect for Ferguson, adding: 'He is always the boss.
'His career is absolutely incredible. He has won loads of titles. He has made Manchester United the best team in England right now and I think he is one the best coaches in the world.'
I'm No 1: The Spanish international has become one of the planet's leading defenders
The defender is also looking forward to meeting up with former team-mate Wayne Rooney, but says their friendship will be put to one side at Wembley.
'With Wayne we always had a great relationship,' he said. 'A while ago I saw him and we were talking about the final. He is always dangerous - he is one of the best.
'We will have to really concentrate and not give him any space, time to think or let him score goals.'
Pique will be reunited with Puyol, who has missed a large chunk of the season through injury, in tonight's game.
The Barca captain is set to start, but may fill in at full-back with Javier Mascherano in line to play in central defence. Either way, Puyol will make sure his young team-mate is focused.
Pique added: 'We know Puyol. He is a really good professional and even if we are winning 4-0 or 5-0, he really concentrates until the game is finished - it is a great experience for me to have him next to me.
'When you have a player like Puyol, who has been for 12 or 13 years at the club and he is playing all the games, it's because he has something (special). When I arrived here I tried to do the best I can but Puyol for me is an example.'
Barca have yet to lose a game this season when Puyol has been in the side.
Rooney backs Hernandez to steal the show in the Champions League final at WembleyBarcelona v Manchester United is the perfect contest. now can they deliver?We will win classic Champions League final, insists United boss FergusonAll the latest Manchester United news, features and opinion
Explore more:People: Alex Ferguson, Nemanja Vidic, Gerard Pique, Wayne Rooney, Rio Ferdinand, Javier Mascherano Places: Barcelona, Manchester, Spain, Germany, United Kingdom