We like to think that great players are born great.
That great players can be great any time, anywhere. Like Roy of the Rovers. And while to a certain extent it's true, it's not as simple as a comic-strip story.
Natural talent is, of course, a big factor in a footballer's career. But there are other things at play.
Diego Maradona is considered to be one of the best players who ever lived. But he was disappointing—as much as Maradona can ever be—during two years at Barcelona before he found a spiritual home at Napoli.
Zlatan Ibrahimovic is one of the most naturally gifted players of his era. But he too struggled at Barcelona.
Maradona and Ibrahimovic could only be truly great when they felt appreciated, happy and comfortable.
Which brings us to Manchester United and Robin van Persie.
You will find few people willing to argue that van Persie isn't one of United's best players. He proved it, if he needed to, last season.
But there have been rumours all season that the Dutch striker is unhappy at Old Trafford, reported by Mike Keegan of the Manchester Evening News as well as many others.
Moyes, so far, has always insisted that's not the case.
And last week he played down the significance of quotes from van Persie after he hinted he wasn't comfortable with United's tactics following the defeat at Olympiacos, per Keegan:
You’re only picking out the big thing. Do you know the whole transcript? I have no problem with it.
If you actually read it I could understand totally where he was coming from. I travelled back from the Holland game with him the other night. I watched him play and I travelled back with him.
The statistics proved before they both (Rooney and van Persie) came back that we only lost one game with them in the team up until the previous run of three or four games.
The record with the two of them in the team was fantastic so I was talking up how good they were playing together a month ago. We didn’t play well at Olympiacos, it was that one game that dragged that up.
Robin knew exactly what was happening. I told him. I walked over and told him that I was going to have to take him off but it was the right decision.
It was a foul (against Reid), but it was not a second booking. It made my job easy.
He played 90 minutes for Holland in midweek and I was never going to play him for another 90 minutes today.
At the very least, van Persie will be at Old Trafford until the end of the season. And, unhappy or not, he will be key to Moyes as he tries to salvage something from this campaign.
Even though he's not been at his best this season, he's still scored 14 goals in 22 games.
But in the summer, the United manager will have a decision to make.
It seems strange to suggest that, in the summer when Moyes needs to sign good players, he might consider letting one of his best leave.
He can dig his heels in and make sure van Persie honours the next two years of his contract. But great players can only be truly great when they are happy and content.
And if van Persie is not, then Moyes will be better off finding someone who is.