Old players and new have watched over the years as the Real Madrid star has become one of the game's best, writes Andy Mitten in Madrid.
Champions League: Real Madrid's Cristiano Ronaldo has world at his feet
Mickey Adams, the Leicester City manager, was briefing his players.
"There's a new Portuguese lad who is out of his depth," he said in the dressing room before his side took on Manchester United in 2003.
"He's young and out of his depth. Let him know what English football is all about."
The Leicester forward James Scowcroft, a lifelong Manchester United fan, took heed of the instructions.
"After five minutes, we hit a long diagonal ball through the air and Ronaldo didn't know what to do," said Scowcroft.
Cristiano Ronaldo watched, unaware that Scowcroft was on his blind side. "He probably wasn't used to balls like that in Portugal," said the player, who headed the ball forward to Paul Dickov.
From the bench, Leicester's assistant manager shouted: "That ball's on all the time". He thought that Leicester could isolate Ronaldo by hitting balls on top of his head. They had done the same thing to Arsenal's Ashley Cole two weeks earlier, to great effect.
Ten minutes later, Scowcroft was about to seize another chance after Ronaldo took a heavy first touch.
"It was a good chance to win the ball back and physically let him know I was there," he said.
"In a controlled way I went to ground thinking that I could win the ball and follow through, while letting him know that he was in for a tough physical battle."
That was the plan.
"Just as I was about to win the ball, with his quick feet and in the blink of an eye, he poked the ball past me and ran around the other side, leaving me to tackle fresh air.
"As I went to ground, I looked over my shoulder and Ronaldo was 20 yards ahead of me. I thought: 'How did he do that?'"
At half-time, the assistant manager instructed Scowcroft to get tighter to Ronaldo. He replied: "You try and get tighter to him. Every time I try, he runs the other side."
Scowcroft will be in the Santiago Bernabeu on Wednesday night, watching from the stands along with 5,000 other travelling United fans as his team play Ronaldo's Real Madrid.
It is the most eagerly-awaited match in world football this year and the callow youth of a decade ago is now the second best player in the world.
"I think he's underrated and doesn't get the credit he deserves," said Scowcroft. "There's a hairline of a difference between Ronaldo and [Lionel] Messi, not the gulf that some imply. He's that good, I don't think United will win tonight."
Michael Reizeger has also played against Ronaldo. The former Barcelona and Holland full-back also thinks he is the key man in the game tonight.
"The problem for United is that you can't man mark Ronaldo," said Reizeger, now 39 and still living in Barcelona. "It's the same with Messi.
"You can't stop them and if you try, they'll switch positions and wreck your formation by taking two men out of the game.
"Players try to get close to him, but Ronaldo doesn't need a lot of space. Against Sevilla on Saturday [when Madrid won 4-1 thanks to a Ronaldo hat-trick], he had around three metres. In that time, he got the power to hit a shot and score from outside the area."
It is the culmination of a talent Reizeger encountered while playing for Middlesbrough in the English Premier League.
"We knew he was exceptionally good," said Reizeger. "I'd played with some of the best players in the world at Barcelona and could see that he had the ingredients to become one of them, to be a big star.
"He was fast, technically good, confident and not afraid. You don't often get those last two qualities in young players.
"People ask me to compare Ronaldo to other players. It's impossible. If you look at the best five players in the world, they're impossible to compare to others. Their differences set them apart from the rest."
Like everyone in football, Reizeger is looking forward to Wednesday's match.
"They're two giants," he said. "Manchester [United] are playing very well, Madrid have struggled away. I know all about Robin van Persie because he's Dutch. He has been incredible for the last four seasons, if not at the Messi/Ronaldo level.
He could move to that level if he can inspire Manchester to win the Champions League. When a player comes to a new team, they usually need time to adapt.
Van Persie needed no time, it's like he's always played for Manchester."
United fans wish also that Ronaldo had always played for their club. They know how good he is. They hope he doesn't prove it again tonight in football's finest arena.
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