Bothered by a nagging groin injury Bendtner has not played since May but had shown signs of returning to match fitness this week when he began training again with the squad.
But the Arsenal forward was back on the sidelines on Friday with Olsen admitting their was little chance Bendtner would be leading the Danish attack against the Netherlands.
Denmark will travel to Johannesburg on Saturday ahead of their Group E opener on Monday against the Netherlands.
"We'd love to have him back of course but I think I would be dreaming to have him back," Olsen told Reuters. "I don't think he will play.
"Surely we hope to have him back (sometime during the World Cup), he is good player, a talented player and we hope."
Bendtner also did not sound optimistic about his chances, saying there is still work needed to gain full match fitness.
The lanky 22-year-old cut a forlorn figure as he was left alone pacing the goal line listening to music on head phones while his team mates ran off to practise on another pitch.
"You want to be 100 percent but you have to take it day-by-day and see what happens," Bendtner told Reuters. "No I am not confident I will play (against the Netherlands), I will take it day-by-day then see how it works and see what happens.
"I am still missing a few things and it is not great but we will see."
Bendtner's place up front is likely to be taken by Jon Dahl Tomasson.
The Feyenoord striker has been a stalwart of the national team and his 51 goals are the second most on Denmark's all-time one behind leader Poul Nielsen.
But Tomasson's touch has deserted him having not scored for Denmark in more than two years.
After scoring in five straight matches, Tomasson has not found the back of net since scoring on penalty kick against Slovenia on February 6, 2008.
