Even the best must bow to Old Father Time

There is a real sadness in watching genius fade, in watching the clock slowly stop. As this northern winter stretches out, the sun is setting on two cricketers thousands of miles away: Sachin Tendulkar and Ricky Ponting.

These two men, one spiky and confrontational, one trapped in a serene mask of national adoration, have been the backbone of international cricket for a generation. Both are brilliant stylists, both have led their countries, both have had to carry the pressure of being the greatest batsman in their side and, at times, the greatest batsman in the world.

Both seemed for so long oblivious to the marching years - so energetic, so athletic - but now time is getting stuck in. Maybe the eyes are fading just fractionally, maybe the reflexes are going incrementally, or the knees, or perhaps the mind or the body is just weary of years of almost non-stop cricket.

Tendulkar has been a star since his Test debut aged 16 and became the first overseas player to represent Yorkshire, at the age of 19, posing awkwardly at Headingley wearing a cloth cap and holding a pint of bitter. No one would dare ask him to do that now. Last year he eventually won the World Cup with India and in between he has broken almost every batting record.

For him, the signs may have been there during the long wait between his 99th and 100th international centuries.

The 100th came eventually, in March, during a one-day game against Bangladesh, but it had taken a year. For a run machine of previously unfailing service, this was worrying.

The batsman who at his best touched the ball with such timing that it was at the boundary before you were aware it had left the bat, was now vulnerable. In his last six Tests he has averaged only 15.30. He suddenly looks exposed against the English spinner. He is misjudging length; he is missing straight deliveries. The banging roar of acclaim is still there when he walks to the wicket, the silence is still total when he is dismissed, but the mood is changing. When he came to the crease at Mumbai, probably his last Test in his home city, there was a sense of anticipation - not that he would score a hundred, but that he would fail again. He did.

Meanwhile, in Australia, the selectors have been forced into defending Ponting's place in the side ahead of the 3rd Test against South Africa in Perth, which starts on Friday. Ponting, one of the most complete of Australian batsmen, is a scrapper and a fighter - only Tendulkar has scored more international centuries. A scrawny chap, he has verve and courage and grit and an unerring instinct to walk to the crease and attack. Like Tendulkar, Ponting started young, playing Test cricket by the time he was 20.

Unlike Tendulkar he has made runs relatively recently - it is less than a year since he had a wonderful series against India, which included a double century.

However, as he enters his late thirties, time is running faster and giving fewer chances. He may have scored piles of runs in the Sheffield Shield but his failures against South Africa loom huge. The press, vocal ex-players, are inviting him to go.

There is a third man, a contemporary of Ponting and Tendulkar, who still has the eyes and the skills, but a crumbling body.

In the past two years Jacques Kallis has averaged 71.04 in 15 Tests - compared to Tendulkar's 38.58 in 18 Tests and Ponting's 34.03 in 18. He bowls too - if anything he is improving. But he has been injured during South Africa's last three away series. Last week in Adelaide, his hamstring went for the first time in his career. He still played two match-saving innings, but he is a doubt for Perth. A stiff neck did for him in New Zealand and in England last summer his back seized up.

One of the most underrated players of all time - perhaps, deeply unfairly, because of his heavy-set build and slightly plodding nature - looks as if he will be defeated by his own physique.

Ponting, Tendulkar, Kallis: together they are the last remnants of a wonderful generation of batsmen that encompassed talents as rarefied as Brian Lara (who retired six years ago) - and as remarkably patient as Rahul Dravid. They deserve better than to flail against the dying of the light.

They deserve to leave triumphant, acclaimed.