What's the first rule about managers conjuring imaginary injuries to suit their purpose? Nobody talks about it.
It's one of the dark arts of the game, and generally speaking almost impossible to prove. Do you really think Ryan Giggs was injured every time he skipped a Wales friendly, or a non-event qualifier?
No? Well prove it then.
For managers fake injuries are the last bastion of deception. Muscle tears and knocks are so intangible to you and I that we'll never know any better, and with the club doctor in on the act there's usually a respectable source validating the whole sting operation.
So if Player X is playing badly and needs to be dropped (let's suggest an out-of-sorts Fernando Torres to keep it interesting), it's far better for everybody concerned if the manager blames a groin strain than comes out and says "he's having a shocker".
The second example, as cited with Giggs, is the scenario where a club manager doesn't want a player disappearing on international duty, or wasting 90 minutes in the Carling Cup. Cue a minor calf injury.
But increasingly common in the modern game is the convenient injury to facilitate emotional recovery. Basically, you've got a player embroiled in a hideous tabloid feeding frenzy and he needs time to pull himself together. If you tell the press, you'll only make things worse. So you make up an injury.
At least that's what Sir Alex Ferguson did to aid Wayne Rooney's smooth passage back from a diabolical World Cup and a messy prostitute scandal. And what did Fergie get for his trouble? The player he protected came out and revealed the ruse for what it was.
"I've had no ankle problems all season," Rooney said yesterday.
"Then why did Alex Ferguson say you had?" asked the reporter.
"I don't know," came Rooney's reply. And then he laughed.
Oh to be a fly on the wall when Ferguson confronts Wazza about that one. You can only imagine the incandescent rage that will descend, and you have to believe Ferguson will give him the hairdryer on full power for betraying him in public.
Rooney had already embarrassed United enough, without dragging their distinguished manager through the mud and outing him as a liar.
At a club that prides itself on being bigger that its biggest stars, Rooney is walking a precarious tightrope. Remember what happened when David Beckham bit back, or when Jaap Stam had a go? Ferguson stayed, they left.
With Rooney struggling for form and the January window approaching, the famously bullish striker may have signed his Old Trafford death warrant.
And even if he stays Ferguson may well be tempted to drag that mythical ankle injury out for a couple more weeks - but this time tell it like is.