Paula Radcliffe is unlikely to defend her World Championship marathon title in August after suffering a stress fracture at the base of her spine.
Radcliffe could compete on the track in Japan
The women's world record holder said the fracture happened when she gave birth to daughter Isla 15 weeks ago.
However, she could compete over 10,000m in Japan, which she describes as a stepping stone towards Beijing in 2008.
"I have been told to take six weeks off from running. It's really frustrating," said the 33-year-old.
"The World Championships is important but I don't see this by any means as my last year at a World Championships, there are more times after that. Beijing is the thing that is more important," she added.
"It's fair to say that I'm not taking huge risks to ensure that I will be in Osaka but I haven't totally ruled it out either. I guess it depends on how much time I have to have off completely."
Asked if the possible of lack of preparation time between now and Osaka might favour her only doing the marathon, she said: "No, I'd say if it's going to throw me anywhere, it would throw me the other way (towards the 10,000m).
"You need less preparation time and coming out and running the qualifying time, as long as you are back running, it's something you can do, you just need a race and you can find those anywhere. I don't see that as a huge obstacle.
"Having said that, I am really not happy, I really miss racing and I want to get back racing as soon as possible."
In Radcliffe's absence, the British marathon team is headed by Jon Brown and Mara Yamauchi.
Tokyo-based Yamauchi finished sixth in the women's race in the London Marathon.
Brown, who has twice finished fourth in Olympic marathons, pulled out of the London race because of a virus.
Peter Riley and Dan Robinson join him in the men's team, although Riley must prove his fitness before his selection is confirmed.
Tokyo-based Yamauchi will race alongside Kathy Butler, Tracey Morris and Liz Yelling in the women's race quartet.
The World Athletics Championships take place from 25 August to 2 September.