Former anti-doping boss Richard Ings expects WADA will need to produce something new and different to win its appeal against a group of Essendon players.
The drawn-out Essendon supplements saga reaches another milestone next week when the Court of Arbitration for Sport (CAS) hears WADA's appeal against a landmark AFL anti-doping tribunal verdict in a closed hearing.
In March, that AFL tribunal cleared 34 current and past Essendon players of anti-doping charges.
Prominent American anti-doping lawyer Richard Young is said to be leading WADA's appeal, which is scheduled to run for five days from next Monday in Sydney.
"A highly-esteemed panel of arbitrators (the AFL anti-doping tribunal) have reviewed all the evidence and found that the players did not have a case to answer," Ings told AAP.
"WADA will have to produce something new and different to convince a group of CAS arbitrators if they hope for a different outcome."
It is understood less than half the 34 players will be at AFL clubs next season.
The appeal is the latest instalment in the mess that started in early February 2013, when Essendon announced they were coming under a joint AFL-ASADA investigation.
The saga is a result of the Bombers' 2011-12 supplements program, with the players insisting they did nothing wrong.
It has caused Essendon severe damage and brought about the downfalls of several prominent figures at the club, including coach James Hird.
The AFL and ASADA have also not escaped unscathed, with ongoing commentary about the investigation and how it was run.
While there is also speculation about various legal actions that might stem from the scandal, the CAS hearing is the last step of the official anti-doping disciplinary process.
Whoever loses the appeal cannot take the matter further.
Even if CAS wins the appeal, the Essendon players might only receive a token ban.
Given they have already served provisional suspensions and the matter has been going for so long, any punishment could be backdated heavily.
But Ings, the former ASADA chief executive, is not sure about Essendon's hope that the CAS verdict might be known by Christmas.
He said CAS can deliver a verdict in a short time frame if there is a pressing matter - such as an athlete competing at the Olympics.
"Here, there's really no pressing time frame," he said.
"The players aren't suspended, they're free to keep on playing.
"Is it possible to get it done before Christmas? I would think that would be very unlikely."
He added the same provision that applied for the AFL anti-doping tribunal - comfortable satisfaction that the players had breached anti-doping rules - would be the test for this appeal.
And it will be a totally new hearing, with WADA and the players able to produce fresh evidence.
"A decision was made at a tribunal and WADA wants to take that decision ... to the next level of arbitration and have them review everything all over again," Ings said.
"So what you have taking place next week is a brand-new hearing.
