I will never forget coming back from a game against Charlton some time after Cristiano Ronaldo had signed for Manchester United and thinking to myself: 'Do you know what? I just give up with him.'
He had been flailing around on the ground, he was never in his position and he was unreliable.
As someone who had played with David Beckham and Ryan Giggs, world-class players who worked up and down and did the ugly part of the game, playing with Cristiano Ronaldo was a constant frustration.
He would go wandering off to the left, to the right, up the middle; he was inconsistent; and he would cost us. I remember him giving the ball away at Chelsea in the Mourinho years and Chelsea scoring.
He would win us a match but then we wouldn't see him for the next game.
I remember snapping at him and going crazy once when he tried to over-complicate in front of goal, with some back-heel flick rather than a sidefoot to finish.
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'What the hell are you playing at?' I said. 'That's not what we do here.'
My patience was wearing thin, as was the other players'. It wasn't that we wanted him out of the team or the club. It was just: 'When will he learn? When he's going to pick up the English game?'
But the experience of Sir Alex Ferguson meant he never lost patience.
He always went with him.
And then I remember when he came back from the 2006 World Cup after all that controversy with the Wayne Rooney red card.
He walked into the dressing room and I thought: 'Jeez, what has happened to him over the summer?'
When he had come to the club he was this thin, wiry boy. Now he was a light-heavyweight. He'd been on the weights over the summer and it was like watching someone grow up in a matter of weeks.
And what ensued for the next two years was astonishing.
I can't believe anyone has ever seen anything as extraordinary in the Premier League.
I know we have had Thierry Henry, Eric Cantona and Gianfranco Zola - and perhaps Henry in his prime came closest - but for two years this was a player on another planet, the best in the world.
He would prey on the weak. He is an absolute bully, as Maicon found out for Manchester City in the Bernabeu this season.
Bully: Ronaldo terrorising for club and countryHe sniffs blood, he will find the weakness in the back four. If he's not getting the left-back in the first 15 minutes, he'll switch to the right-back.
If he's not getting the right-back, he'll switch to the left centre-back.
He'll find someone in your back four who is weak and doesn't like defending one on one and against pace and power.
His skill, strength and speed were incredible.
I had played with some great players in Roy Keane, Ryan Giggs, Paul Scholes, David Beckham, Eric Cantona and Mark Hughes.
Old Trafford legends: George Best (left) and RonaldoBecause of their longevity at the club, they may be ranked above Ronaldo as United greats.
But no one was a good as Ronaldo in that two-year period.
I was injured for the 2007-08 season when United won the Champions League, so was in the stands for many of the games.
I remember thinking: 'How could it have been better watching George Best?'
I never saw him play but I thought: 'If it was anything like this I understand why people are still talking about him.'
No one was as good: Ronaldo will go down as a legend at Old TraffordAnd no one is ever telling me he isn't brave, by the way. No one's telling me he's soft. He wouldn't hide in games even though he knew that the first thing every team wanted to do was to leave one on him.
Yes, he went down too easily at times, especially in his early years. But if he had a 14st centre-half bearing down and about to take his knees out, he was told by us and the manager: 'Stay away from those challenges.'
We didn't want him injured.
Look at the headed goal he scored at Roma in 2008. He was laid out by the defence as he attacked the ball. You don't score a header like that unless you're brave. That was in the mould of Frank Stapleton, Joe Jordan, Andy Gray or Mick Harford.
Brave and strong: Andy Gray (left) and Frank StapletonHe's not some soft flaky character, he's a hardened player.
It got to the point that as right-back in that 2006-07 season I never complained if he could go off for 30 minutes and leave me two on one.
He completely changed my opinions about the game.
I'd always been taught that I must have a right winger in front of me. But I knew he'd go and win us the match.
Different kind of player: Sir Alex Ferguson watches Ronaldo trainDarren Fletcher would say that we'd have to work around him, because he'd always do more harm than opposing players he was leaving free to go forward.
As a 27-year-old at the time, an experienced figure, I was expecting to tell this 21-year-old how it was.
And he was telling me something completely different. I'd been playing with my blinkers on for years but he made me open my eyes to different ways of playing the game.
I'll never forget coming in training one day when the session was eight hard runs but, for the last two, he seemed to be taking it easy.
He simply said: 'Too much water kills the plant.'
Even today I remember those words.
I'd always been brought up to believe that every single minute of every day was a fight and that you had to battle continuously, even in training.
But though he would work hard, he would train with efficiency. If there were eight runs and he'd done six well but felt that was enough, he'd do two at his own pace. He knew his own body.
So who was the wise one?
All the premeditated tactical theories I had learned about getting and staying in your shape, and tracking back with your runner, all the things that had been drummed into me, were thrown out over those two years because we had a player who could make up his own rules with the blessing of his team-mates.
He has helped to redefine the game by creating a new breed of flexible forward.
In that 2008 team with Paul Scholes, Wayne Rooney, Ryan Giggs, Carlos Tevez, Nani and Ronaldo, the forward players could be anywhere in that front line.
Fantasy Football: Ronaldo spearheaded an attack comprising the likes of (clockwise from above left) Ryan Giggs, Wayne Rooney, Carlos Tevez and Nani
You couldn't say before the game: 'I'm playing against him today'. It was a different way of playing and understanding modern football.
He was always fascinated with becoming the best player in the world.
He would have no concerns about telling us in the dressing room or the media that that was his goal.
In England, that kind of ambition can be drummed out of you.
The team ethic is so important, sometimes we stamp on such individualism.
But he believed in the team ethic. He also believed that the team would be better if he was the world's best.
You would always say individual honours aren't important, but Ronaldo was different.
To him they were.
He wanted the medals on his chest and he would get angry when either he or the team weren't performing to that level.
Changing the thinking: Individual honours matter to RonaldoAgain, he changed my thinking. He showed it is possible to accommodate that kind of individual ambition within a team and marry the two together.
To be able to leave United in his prime and still have his name sung by the fans tells you something.
On Wednesday night, he will be at Manchester City, his first return to the city since leaving United.
While he may receive the kind of stick reserved for former United players, everyone in that stadium, including me, will be thinking: 'I'm watching Cristiano Ronaldo tonight'.
If you're a kid, it will be a reference point, something to talk about when you're older.
But, to be honest, for anyone who appreciates football, it will be a privilege to watch one of the great players of all time.
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