Nine months ago, Belgium's Kirsten Flipkens stepped off a flight from Thailand and felt like her calves "were about to explode".
Used to pain as a professional athlete, Flipkens shrugged it off and played another tournament that week, but eventually consulted a doctor, to be told she had blood clots in both legs.
"I didn't think in the beginning about blood clots so I was still playing and getting treatment," world number 43 Flipkens said.
"Two days after, I was supposed to leave for Japan for the Fed Cup and the doctor told me: 'if you step on the plane, you will probably come out of it blue'. That was the moment I was getting scared."
On Friday, Flipkens reached the last 16 of a grand slam for the first time on Friday with a 6-2 4-6 6-3 win over Valeria Savinykh of Russia.
Now, getting on a plane is almost like a military exercise for Flipkens. On go the compression socks to combat deep vein thrombosis (DVT) and then, if the flight is longer than three hours, she has to take blood thinners.
"The blood thinners are by injection, in the belly," she said. "Once you get used to it, it's fine but in the beginning it's the worst."
It was a tough time for Flipkens, whose ranking slipped from 182nd to 262nd and who was struggling to break through to the elite of the women's game.
But things became even worse when just a couple of weeks later, the Belgian Tennis Federation decided to take away her funding because her ranking had dropped.
"I found out in April about the blood clots and at the end of April they decided not to support me anymore," the 27-year-old said.
"For me it's finished. Even if they come back now to help me or whatever, I don't need their support anymore. I'm happy now that I found my structure, that I have a new coach, and that I am the player I am today.
"Normally if you have such a long relationship already, they should also be there in the rough times but if they lose their support and their trust in you, it's their choice. I proved them wrong."
Whether that was the catalyst for her rapid improvement, it was certainly a turning point.
Returning to the WTA Tour last June, she beat Sam Stosur and Roberto Vinci to reach the semi-finals in Rosmalen and then won her first title, in Quebec City.
By the time the Australian Open began, she had broken into the top 50 for the first time and reaching the last 16 of a grand slam is sure to see her rise even further.
"Maybe if that (the funding cut) didn't happen, maybe I wouldn't have played as well as I do now, you never know," Flipkens said.
"It (the blood clots) changed me in a way. I realised that life is not for ever and nobody knows when the end is, so you have to enjoy every moment and try to do what you like to do.
"In life I am just really happy that I am still enjoying every moment and that I'm on court. I'm the same person as before but I am just really happy to be here and play my best tennis ever."
Last August, Flipkens was aided in her comeback by former world number one Kim Clijsters, who helped her practise and almost worked as her part-time coach.
"She's like an older sister to me," Flipkens said. "I've known her already for so many years, 20 years and we've been in the same boarding school, we've been in the same tennis school, our mums are best friends.
"She and a few sponsors were the only ones who didn't let me down last year in May when I was only 262 in the world. I was 26 at that time, so it's normal that a lot of people didn't trust in me but I'm a fighter and I didn't give up."
With Clijsters in the wings and with her ranking heading inside the top 40, how far can she go?
"I think the top 10 is maybe too high - to play against these girls like Serena Williams) and (Victoria) Azarenka, it's just a different level because they're playing too good, too aggressive to play my kind of game against them.
"But I can play top 20, top 30. If you're in the (fourth round) in a grand slam it means you can play a good level.
"But to have your job as a game you love to play, is the best job in the world, I think."