Rio Ferdinand personifies the difficulties of building a united front in the battle against drugs in sport.

In the past month a top athelete, Dwain Chambers, was banned for two years for failing a drugs test.

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Britain's number two tennis player, Greg Rusedski, also failed a test but he was let off because of extenuating circumstances.

England international Ferdinand did not fail a test, he just failed to turn up for one shortly after this soccer season started.

The world's most expensive defender was banned for eight months, a decision that was upheld by an independent appeal panel on Thursday.

So Chambers misses the Athens Olympics and faces becoming a sporting pariah.

Ferdinand's absence has already crippled Manchester United's attempt to retain their league title and he will also miss playing for his country in the European Championship.

Rusedski, however, is free to carry on playing, like seven other players who failed tests for the banned substance nandrolone, almost certainly because they took electrolytes that officials from the men's tour gave out early last year.

These anomalies in treatment and sentencing were meant to be a thing of the past after January 1 when the World Anti-Doping Code came into effect.

The World Anti-Doping Agency (WADA), the body which launched the new code, said Ferdinand was lucky to escape a two-year ban which is mandatory for serious doping offences under the code.

However, FIFA, world soccer's governing body, is yet to sign up to the code. Tennis has signed up but the women's WTA, men's ATP and the ITF governing body all conduct their own tests, and apply their procedures depending on the tournament concerned.

FIFA president Sepp Blatter has promised to sign on the dotted line before the Athens Olympics -- otherwise soccer will be excluded from the Games -- and he said he was shocked that Ferdinand's ban had not started immediately.

The rangy defender failed to turn up for the test in September. The independent disciplinary commission did not sit until December 19 and his ban started only on January 20.

WEAKENED IMPACT

Blatter told Prime Minister Tony Blair this month that the handling of the Ferdinand affair was a "textbook" example of how not to deal with a doping matter.

However, Blatter has weakened the impact of the code by insisting that each doping case is treated on an individual basis, allowing special circumstances to be taken into account.

This is how Rusedski escaped as the code, if invoked in its pure form, rests on the principle of strict liability whereby athletes are responsible for everything they eat and drink.

For more than 20 years athletes taking performance-enhancing drugs have easily kept ahead of the testers. The Athens Olympics in August will show whether the tide is turning in favour of those athletes who prefer to stay clean.

Developments in the United States, where the government and leading sporting officials finally appear determined to tackle the doping problem, and scientific progress have definitely sowed concern among the drug-takers.

The development of a test for the designer steroid THG, before the vast majority of athletes even knew the drug existed, caught many including Chambers by surprise.

Other drugs tests could be in place by the Games in August including one for human growth hormone, believed to be widely used in strength sports.

The storing of samples, so they can be retroactively tested when tests are developed, will also cause potential drug-testers to pause and work out their chances of escaping detection.

However, until the wrinkles are ironed out of the anti-doping regime, the guilty may be allowed to escape and the innocents will continue to suffer unfair competition.