During Sir Alex Ferguson's tenure as Manchester United manager, he has seen many great talents walk through the doors of Old Trafford.
The likes of Eric Cantona, Paul McGrath, David Beckham, Ryan Giggs, Roy Keane, Ruud Van Nistelrooy, Paul Scholes, Wayne Rooney, and Rio Ferdinand have all been tutored by Ferguson. I'm sure you could name twice as many great players I have left off this list as well.
They all had prodigious talent, but one of the things that made Ferguson such a great manager was that he was never afraid to let them go if he felt their time had passed, or if they were having a negative impact on the team.
And he is usually right. In fact, he has said that the only player he has ever regretted selling was Jaap Stam.
He sold David Beckham while in his prime, Roy Keane, described by Fergie himself as the best player he has ever coached, and Paul McGrath, widely considered to be one of the best defenders to play in England. Not to mention Ruud van Nistelrooy, one of the most prolific strikers of recent times.
There is no way he can be accused of being afraid to ship out big names.
Or is there?
Cristiano Ronaldo's form this season has been a shadow of the dazzling form he showed last year.
Of course, it would be unrealistic to expect him to repeat that form so consistently, but this year he has been largely disappointing.
It isn't his poor form Fergie should be so worried about, however. It is his attitude.
Much has been made of this, but it is becoming more evident as the weeks go on that Cristiano Ronaldo is, at times, harming the team.
If we look at two recent games, he is responsible for two big goals being conceded.
Against Aston Villa, he was tackled after dwelling on the ball—fine, everyone makes mistakes.
What wasn't fine, however, was that he stood still and sulked, instead of chasing back and being determined to get the ball back for his team, like Rooney would have done, for instance.
That led to a goal from Aston Villa to put them ahead, 2-1.
Against Porto, with just four minutes on the clock, Ronaldo carelessly gave the ball away again. Did he chase back and try and get it?
No. Instead he watched as his mistake, then failure to atone for his error, led to Porto getting a vital away goal.
United now have a mountain to climb if they want to progress to the next round.
It may be that, after going so long without conceding a goal, Ronaldo has full confidence in his defence, and so feels he doesn't need to chase back.
That excuse doesn't wash with me. United have conceded bucket-loads of goals in recent games, so that confidence, if indeed it was that and not just laziness, should be well and truly shattered.
I can't help but feel that his attitude is hurting United, and therefore Ferguson should get rid of him.
But I can't see that happening, not even with the Real Madrid saga ready to start up again.
I think Sir Alex has found a player that is just too good to sell because of a bad attitude.
None of the players he has sold before managed to win a World Footballer of the Year award. Cristiano Ronaldo, therefore, is arguably the best player Ferguson has ever coached, in terms of ability.
In terms of attitude, however, he must be up there with the worst.
Yet Fergie knows that he can always come up with that moment of magic.
For example, in the aforementioned Aston Villa game, Ronaldo scored two goals, playing as big a part as Federico Macheda in United's crucial win. He knows that, for all his bad points, Ronaldo can pull a rabbit out of the hat at any time.
Then again, so could Beckham, Keane, McGrath, and Van Nistelrooy.
It bears many similarites to the situation between Sir Matt Busby and George Best 40 years ago. Best's drinking problem was having a negative affect on the team. In Sir Bobby Charlton's autobiography, he says the players were always worried that Best wouldn't make it in for training—or even a match.
Busby knew Best was a special player, and so he made allowances. There were different rules for him.
Ferguson may be doing the same for Ronaldo. Could it be that he thinks Ronaldo is irreplaceable?
If so, then I think he is wrong.
In my opinion, Rooney is a better player than Ronaldo. Ability-wise, Ronaldo is probably only surpassed by Lionel Messi in world football. However, Rooney's attitude, in terms of wanting to help the team, is second to none.
I would rather have Wayne Rooney in my team than Cristiano Ronaldo any day of the week.
Rooney always gives 100 per cent effort, while Ronaldo rarely hits that mark, and that is where they differ.
However, I think Ferguson has finally found a player he thinks is too good to get rid of in Ronaldo, even if his attitude is a problem.
Fergie has always been good at dealing with big names, but Cristiano Ronaldo may just be too big for even Ferguson to consider selling.
Is he bigger than Manchester United? No way. Is he too big for Sir Alex Ferguson? I think he might just be.