Australia's women are the reigning Olympic and world 4x100m relay champions, but their coach will be surprised if they retain that crown at this month's world championships.

Shane Rollason, the coach of Olympic 100m champion Jodie Henry and also of the Australian women's 4x100m and 4x200m relay teams, has questioned the depth of the 4x100m squad.

Henry and fellow Australian Libby Lenton, who upstaged Henry at the Commonwealth Games last year, are among the event's elite.

But the Australian with the next-fastest time to her name, Alice Mills, failed to qualify for the team.

It leaves Rollason with concerns over the third and fourth members of the relay outfit, who he said would be considerably slower than their US and German counterparts.

"I'm not going to mince words, we need some people on those relay teams to absolutely step up," Rollason said.

"And I don't think we can be looking at Libby Lenton or Jodie Henry for that, it's got to be the others.

"If they can't do it, it's just not going to happen."

Rollason said Australia's contenders for the last two spots were currently "well behind" the level they needed to reach.

Among them are Queensland's Melanie Schlanger, whose personal best time in the 100m is 54.94 seconds, Victorian Shayne Reese (55.09s) and Lara Davenport (55.82s) of NSW.

"I think we've got girls there that are capable of stepping up, it's whether they can step up in the next 14 days or not," he said.

"There are signs there of people on the improve, but it's just whether they've got time on their side.

"In six months' time it all could be looking good again.

"But we really need someone who can swim 54.5 (seconds) in that relay team on that night.

"If we can get two others that can swim 54.5 then we're going to be in with a much better chance than what we are at the moment.

"But at the moment we're looking at people who can only swim 55.5, so it's a big difference."

Germany holds the world record in the event, but Rollason tipped the US as gold medal favourites.

"The Americans are much stronger now depth-wise," Rollason said.

"Looking at them from a relay point of view I think they're the team to beat in the 4x100m, even though they're not the world record holders."

Rollason said the good news was if Australia could not pull a rabbit out of its hat in Melbourne, it still had plenty of time to rise to the challenge before next year's Beijing Olympics.

"It just depends on how you react, you either stand up or you don't," he said.

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