Michael Carruth, development officer with the Irish Amateur Boxing Association and Olympic champion, said the obstacles O’Reilly faced were “too big” to expect him to make the ring on Friday.
The 23-year-old middleweight from Portlaoise Boxing Club formally lodged an appeal against his suspension over the weekend and is understood to be arguing that his use of the banned substance, discovered in a doping test carried out just before his departure for Rio, was an innocent mistake.
However, the appeal is likely to take several days, and athletes face a very heavy burden of proof if they seek to use the defence of accidental consumption.
“If it is a mistake, it’s the biggest mistake of his life,” said Mr Carruth.
O’Reilly, who has instructed a legal team in Ireland, remains in Rio, where team members insisted the affair was not affecting their morale.
The team got off to a good start when the first boxers out, Ballymena welterweight Stephen Donnelly and lightweight David Oliver Joyce of Athy, comfortably won their bouts yesterday.
Speaking afterwards, he brushed off suggestions that the controversy had upset the team.
“I don’t really know much about that. What we have to do is focus on our own game,” he told RTÉ.
“The spirit in the camp is fantastic. It hasn’t changed at all. We’re all going for gold and we’re all happy. It hasn’t affected us one bit.”
High performance coach Eddie Bolger declined to comment on the affair, but said: “It’s a great week for Irish boxing. We’re here to compete and that’s all we’re focusing on and enjoying every minute of it. We’re all in good spirits.”