The build-up to the start of the Olympic Games in just 11 days time is set to be clouded in uncertainty after the International Olympic Committee yesterday took the surprise decision to back away from imposing a blanket ban on Russian competitors despite the weight of evidence, produced last week in a report by Canadian investigator Richard McLaren, detailing the state-sponsored system of doping in place in the country.

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In a vote described as taken “unanimously - with one exception” by IOC president Thomas Bach, its Executive Board has effectively thrown a red-hot poker at the ruling federations of each of its 27 sports and ordered them to catch. It is they, not the organisation charged with safeguarding the integrity of the Games and its athletes, who must now decide on the fate of every single member of the 387-strong Russian team named for Rio.

Each, the IOC trusts, will be scrutinised to prove they are clean beyond reasonable doubt with the federations asked to “carry out an individual analysis of each athlete’s anti-doping record, taking into account only reliable adequate international tests, and the specificities of the athlete’s sport and its rules, in order to ensure a level playing field.”

That, even Bach acknowledged, may be an impossibility before the cauldron is lit inside the Engenhão Stadium on Friday of next week. The IOC’s process requires an initial clearance – then scrutiny from the arbitrators at the Court of Arbitration for Sport - and then a final right of refusal before any entry is accepted.

“This is a very vicious time line but we had no choice,” Bach insisted. “We had this report compiled in about 60 days and we had to react to it in a short time limit. But on the other hand, after the Olympic summit, where we have already indicated the concept of the presumption of innocence and the criteria of only taking international anti-doping testing into consideration, many federations have already undertaken a great effort. And I think they will be able to produce their documents in the next couple of days.”

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Such haste will depend largely on the willingness of each sport to put its own processes under the microscope and the level of suspicions harboured. The International Tennis Federation immediately cleared all seven Russian entrants following the IOC ruling. McLaren found weightlifting , canoeing and rowing to be heavily infected by covered-up positive drugs tests. Their governing bodies are thought likely to act decisively to follow the legally-tested precedent set by the International Association of Athletics Federations in wiping Russia from its entry list.

Others are prevaricating with Russia’s brazen sports minister Vitaly Mutko confident “the majority” of his compatriots will get clearance. The UCI, cycling’s overlords, offered no immediate dissent. While Marius Vizer, the president of the International Judo Federation, was on record last week as favouring a laissez-faire stance, saying: “The presence of Russian athletes is very important as the Russian Judo Federation is a prominent member of the International Judo Federation, with Russian judo playing a great role in the history of sport.”

Bach and his star chamber were accused by former Olympians of threatening the credibility of their own product by opening the door to Russians standing atop the podium while a sceptical audience ponders whether their performance has been fantastic or fraudulent. “What a cop-out,” four-time Olympic rowing gold medallist Matthew Pinsent asserted.

The IOC must fear they will reap the backlash of sowing such discontent, even if they raised the stakes by banning any Russian who has ever served a suspension for doping, even if their sentence has now been served. This, Bach claimed, will send “a message of encouragement for the clean Russian athletes that they have the chance to show they are clean and participate in the Olympic Games – and then serve as a positive role model in the fight against doping in Russia.”

Swimming’s world champion Yulia Efimova is the biggest name now black-listed. However, that the sanction does not apply to other nations will seem unjust with the presence of twice-banned American sprinter Justin Gatlin an affront to many.

In an additional move, Bach controversially closed the door to certain Russian athletes competing under a neutral flag, effectively barring middle-distance runner Yuliya Stepanova who won admiration for her whistle-blowing role in exposing an extensive web of cheating that led all the way to The Kremlin.

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The CEO of the US Anti-Doping Agency, Travis Tygart, last night said the move was “incomprehensible” and would “undoubtedly deter whistleblowers in the future from coming forward.” Improbably, Bach will invite now Stepanova and her husband to watch the action in Rio as guests of the IOC. Whether her compatriots travel in numbers to take part, and whether the global audience finds that repugnant, remains anyone’s guess.