Paula Radcliffe has admitted she may never be able to compete again after complications with a foot injury left her struggling to run.
The British world marathon record holder, 39, has not run beyond a short jog for eight months, since she was ruled out of the 2012 London Olympics.
She said her hopes of competing in a 10km race in the spring of 2013 had been shattered.
"Targets have gone out of the window," she told BBC Sport.
Radcliffe hopes to end her career with at least one more competitive outing, but knows it is not guaranteed.
"I'm very much in that limbo where I know and accept that realistically it may not be possible," she said.
"But at the same time I have a little window of hope and I would rather be able to finish my career in a race, rather than a race I can't actually get to the start line of."
Radcliffe is one of Great Britain's most well-known female athletes.
Despite effectively running for 18 years with a broken bone in her left foot, she was world marathon champion in 2005 and twice won the world cross-country title.
Next month marks the 10th anniversary of her setting a stunning new world record, a mark which she still holds today, when she completed the 26.2 miles of the London Marathon in two hours, 15 minutes and 25 seconds.
But victory on the biggest athletics stage of all, the Olympic Games, eluded her.
She was fifth in the 5,000m at Atlanta in 1996 and fourth in the Sydney 10,000m four years later before disappointing in the marathon in 2004 and 2008.
The dream of competing in front of a home crowd at the London 2012 Games and she had foot surgery on 22 August last year.
"My target when I had my surgery was to run at the World Cross-Country Championship [which took place in Poland on Sunday 24 March], which I would have loved to have done," she said.
in the spring, but a serious setback left her wondering if she would ever run again.
"It was probably looking pretty bleak in December. I was really starting to severely worry if I was actually going to ever get back to running, even for pleasure," added the mother-of-two.
"I've not even been able to run after the kids in the last few months, and you start to think about the first goal - to get back and be able to have a normal active life and then worry about if I can get back to competing.
"In all honesty with me, it was probably always going to be something going wrong with my body that would make my career start to wind down because I am always going to want to keep competing and keep getting out there.
"I would love to be able to run a couple more marathons before I finish, even if it's just another half marathon.
"At the same time I would still like to have a healthy foot in 20 years' time."
Radcliffe talks about returning to running in April, but still walks gingerly.
"To be able to get out of bed in the morning and walk straight away would be nice," said the athlete who won BBC Sports Personality of the Year in 2002 after claiming 5,000m Commonwealth Games gold in Manchester.
"It's just day by day. It doesn't really change what I'm doing. I need to get the foot strong just to be able to walk around and to be, hopefully, able to go for a jog."
Radcliffe had a screw holding her bone in place and an operation to remove that.
"Before I had the screw out I did get back to doing little tiny bits of jogging but you are talking four or five weeks before the Olympics since I've had a run and enjoyed a run," she said.
"Since then I've had a second operation to take the screw out and remove a lot of scar tissue. It's now looking encouraging, and certainly there's a lot less pain walking around, and I'm able to develop foot strength with a view to getting back running in the next couple of weeks I hope.
"It certainly has been a long process and a lot longer than I thought it was going to be back in August. It is a case of letting everything settle down and get strong again before I start to stress it again running. When I do start running, I want it to be something that I can keep doing."
The original injury dates back nearly 20 years and has blighted Radcliffe's career, despite her success.
"I had a collapsed arch which led to a stress fracture in 1994, which took nine months to diagnose," she said.
"The foot was basically knackered. It was a really big operation that they did on it. Basically I'd been running on a non-union stress fracture [a broken bone which fails to heal] for about 18 years and has been causing damage. That's now repaired and healthy.
"It looks a healthier foot but it was a big operation. I was warned it would take a year to settle down.
"I never realised until 2007 when they actually scanned it that all that time I had been running on essentially still a broken bone. It had become stable and had settled down and it's not like I was running round saying 'ow,ow,ow', in pain all the time.
"I always ran with orthotics [foot supports] and always knew that I needed to. It would just get achey and sore with different types of weather.
"All the time I was developing severe osteoarthritis in that joint, which is what has caused the problem in that joint now.
"If we'd had the scans then that we have now then maybe that wouldn't have gone undiagnosed for so long and wouldn't have caused these problems."