Injuries only quicken the decline and Rooney has endured lengthy lay-offs after metatarsal ankle ligament injuries.
I suffered a broken leg and a ruptured Achilles tendon, as well as the pulls, strains and knocks that are commonplace for every footballer. The truth is, every injury and lay-off has an effect. One may be imperceptible, but the cumulative effect gradually dampens the spring in your step, curdles the fluidity and explosiveness of your stride, stiffens and tightens your muscles and disturbs the connection between the speed of your thought and the movement of your feet.
It's hard to accept. You fight it. Put it down to that pain in your ankle or the twinge in your groin. Put in extra hours in the gym or on the training pitch so the sharpness that has dwindled might return. But in reality, it's just part of the inevitable decline.
So what can be done? Change your game. There were spells towards the end of my career when I happily moved to centre-back. Reading the game and organising those around me became far more comfortable than those races with fleet-footed wingers I once enjoyed.
That is why we see Rooney dropping deep, playing the orchestrator in midfield rather than the runner up front. He knows deep down that he can't affect the game as a striker in the way he once did. You either have to learn to play your position differently, or change it. Rooney clearly wants to play in midfield, but your manager won't always accommodate your wishes.
Jose Mourinho has stated -- foolishly, it now appears -- that Rooney won't play as a midfielder in his Manchester United team. Yet as he drops deeper in every game that leaves him in limbo: without a definable role in a sport that has evolved dramatically as he has aged.
Rooney is deserving of a respect to match that of any footballer in this country, and it would be foolish to write him off just yet. But as he approaches his 31st birthday, England and Manchester United's captain will know in his heart that he has to adapt if he wants to survive.