Barcelona defender Gerard Pique admits he had to quit Manchester United because their defensive pairing of Nemanja Vidic and Rio Ferdinand "is the best in the world".

Pique said: "At United, I had instilled in me a philosophy of hard work and sportsmanship to keep for my entire life. Playing in Europe as a 17 year-old was a dream come true.

"But I had to leave. In my position were the best pair of central defenders in the world: Rio Ferdinand and Vidic."