Ryan Giggs claims Rio Ferdinand was taunted for being "one of the worst players in training" when he arrived at Manchester United in 2002.
The Red Devils paid £30million to bring Ferdinand to Old Trafford from Leeds United in what was a world record deal for a defender.
The former England defender went on to become a club legend by winning nine major honours in 12 years, including the Champions League in 2008.
But ex-teammate Giggs claims it took time for Ferdinand to settle at the club and recalls United stars mocking him during training sessions.
Asked about the mentality required to succeed at United, Giggs told beIN Sports: "I used the example of Rio Ferdinand, he was a brilliant player when he came to Man Utd.
"But all of a sudden he’s one of the worst players in training in the boxes we used to play, the little keep ball 8 vs 2 and he’s thinking 'wow'!
"All of a sudden you are under pressure before training has even started because that’s part of the warm up.
"He wouldn’t get the mick taken out of him at Leeds or West Ham if he was in the middle. At United it was constant.
"If you are in the middle they are putting the bib on you, just keep it on, and instantly you are probably going home thinking 'what’s just happened there? I used to enjoy training!'"
Despite Ferdinand's rocky start to training sessions with United, Giggs admitted he was one of the top performers as he grew in stature at the club.
He added: "You have to step up to that next level. There is no hiding place. And he cost £30million, the most expensive defender in the world. It didn’t matter.
"And of course by the end of it he was the best. He was the best in the box because he was so good with his feet, he was confident so there is a bit, or was a bit, of sink or swim."
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