Mullen has until January 31 to request a B-sample of the November test in which he allegedly tested guilty to the rare anabolic steroid Drostanolone.

Newcastle chief executive Matt Gidley indicated on Tuesday, after both he and Mullen had been told of the test result, the five-eighth would take up that option - in which testing usually takes around three weeks.

And while Ings stresses the importance of Mullen having the right to the B-sample and the case still having a long way to go before a final verdict, he says Mullen could be facing a tough and extensive challenge.

"The B's almost always match the A's," Ings told AAP on Wednesday.

If that comes back positive, it's likely to only be the beginning of the process for Mullen, who will continue to have the maximum four-year suspension hanging over his head.

The 211-gamer would then have a chance to provide an explanation and the source, if he is to ultimately beat the charge and suspension, or even have it lowered to two years or a warning.

"To get it reduced down to a warning you've got to prove that you have absolutely no fault at all," Ings said.

"No fault means that you did absolutely everything you could possibly do to avoid ingesting the banned substance, and that's very tough to prove."

Ings stressed ignorance could also not be used as a defence.

"We've seen that in the Essendon case, we've seen that in the Sharks' case," he said.

"Ignorance is not an excuse, particularly at the professional athlete level.

"There are endless examples of athletes who didn't know but were expected to know and received significant sanctions."

The process could also take up to a year given the number of steps available for appeal of ban or sentence.

Any NRL player found guilty would likely face the league's anti-doping tribunal, which also has an appeals tribunal if required. Matters can also be taken to the Administrative Appeals Tribunal, the Federal Court or even the Court of Arbitration for Sport.

"If they were to pursue every single one of those steps then it could take a year or more to resolve," Ings said.

Drostanolone was originally used for breast cancer treatment to help lower estrogen in the body.

However it has since become more commonplace as a steroid amongst bodybuilders, where it is also known as Masteron as it increases muscle growth for lean individuals.

Only two people are currently facing bans in Australian sport for the drug, a baseballer and bodybuilder, while a third is also banned for four years for the use of its metabolite.