Gary Neville admits he moaned about Cristiano Ronaldo in his early days at Old Trafford because he was too "erratic"
The Portuguese star moved to Manchester United in the summer of 2003 for just over £12m from Sporting Lisbon.
But Neville recalls letting off steam to the club's strength and conditioning coach, Mike Clegg, because he struggled to deal with Ronaldo's unpredictability.
He accused the now 35-year-old of struggling to fit into a defensive structure and not delivering when he should've.
Ronaldo went on to become a world star at United following the World Cup in 2006 with Sir Alex Ferguson and Carlos Queiroz earning praise for persevering with him.
And Neville admits it was an incredible transformation to watch.
He told Sky Sports: "Sir Alex Ferguson and Carlos Queiroz, I think it’s important to put Carlos Queiroz in the category with Sir Alex, they were both champions of him, they both believed in him.
"I think that he came back from the World Cup that summer it was like everything had changed. His maturity and his decision-making, which was a big thing, his experience, his physical attributes had completely changed overnight.
"He went from someone who, if you look at his early pictures at Manchester United, he was scrawny, really thin, wiry, didn’t look very strong.
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"All of a sudden, I think it was after that 2006 World Cup, he came back like a super-middleweight boxer. His body had just completely transformed, he was absolutely incredible.
"From a strength point of view and a plyometric point of view, the ability to leap, the ability to score with his head, the ability to change direction, everything seems to fall into place. It was just a maturity, physically, mentally, everything happened to him.
"It was brilliant to watch, there was a point I remember going into the gym after one training session and speaking to Mike Clegg [United’s strength and conditioning coach] who worked very hard with Cristiano physically in the gym and saying to him, ‘I don’t know what he’s going to do next’.
"You didn’t know where he was going to be defensively, you didn’t know when he was going to release the ball, players in the middle of the box didn’t know when he was going to cross it. It was just erratic.
"But they had great faith in him, Sir Alex Ferguson and Carlos Queiroz, and they believed in him, put him forward in front of players who had greater reputations at the time and he developed into something brilliant."
