LONDON (AP) — In April last year, Kirsten Flipkens was diagnosed with life-threatening blood clots in both her legs. On Tuesday, the bespectacled Belgian reached the Wimbledon semifinals.

"It's amazing, it's more than a dream come true to be in the semifinals of a Grand Slam, it's ridiculous," the No. 20 Flipkens said. "Last year I did not even get into the qualifying at Wimbledon. I was 260th in the world and today I am in the semifinals of Wimbledon. It cannot be better. I still cannot believe it. I am so happy I cannot imagine myself waking up. "

A former Wimbledon and US Open junior winner, Flipkens upset former Wimbledon champion Petra Kvitova 4-6, 6-3, 6-4 to advance. Playing in her first Grand Slam quarterfinal, she made only five unforced errors in a gutsy performance. She fell face-first on the court and kissed the grass after closing out the match with an ace.

"I never expected this to happen in my life," she said. "Being in the semifinals of a Grand Slam, of the biggest tournament throughout the year, it has no words. As I said, I never expected I would be able to come and get this far, so far."

It was after a long-haul flight that Flipkens felt the acute pain in her legs and was diagnosed with her condition last year. As a result, she missed two months of competition and her ranking nosedived dramatically, slumping to No. 262.

"Maybe I start to know what's important in life," she said after taming the No.8 Kvitova. "I think winning or losing a tennis match doesn't make a big difference. I mean, if you lose, you have a next tournament next week, so... I just start to see things in perspective."

Flipkens, who had never advanced past the third round at Wimbledon before this year, is clearly on an ascending path. Now training with former No. 1 and fellow Belgian Kim Clijsters, she reached the final at Rosmalen - her Wimbledon warm-up tournament - after losing in the Australian Open fourth round to Maria Sharapova earlier this year.

Thanks to her good run of form, she is No. 20 in the world.

"I think I've been through a lot of ups and downs throughout my career," she said. "I've had so many injuries. Even after the juniors. I was a world champion junior. The year after I had a really bad back injury. All doctors said my career would have been over normally. But I'm just the kind of person that doesn't like to break, and I keep on fighting back every time. "

After beating Kvitova under the retractable roof of the Centre court, Flipkens paid tribute to Clijsters, who had shared her emotions on Twitter after her protegee's win: "Still drying my eyes :-)) So proud of how @FlipperKF handled the big occasion for the first time!", Clijsters wrote.

Flipkens, who will next play France's Marion Bartoli, gave credit to the former four-time Grand Slam winner for reviving her career.

"She's in America, but she's been there for me through the good and through the bad times," she said. "Of course, I have to thank her for still believing in me."

Flipkens became the first Belgian to reach the Wimbledon semis since Justine Henin in 2007. That year, Henin lost to Bartoli.

"I never played Marion, so I really have no idea," Flipkens said. "I don't really know what to expect."

The 15th-seeded Bartoli will be on her guard too.

"She's behind me in the rankings, it's surprising to play her in the semifinals. But she beat Kvitova, she is extremely dangerous," Bartoli said. "She came to prominence very early in the juniors because she was very strong and won a lot of titles. Then she had a lot of injuries and was under a huge pressure in her own country because people saw her as Justine and Kim's heir. It must have been difficult to cope with that."