Sorana Cirstea achieved "the biggest comeback" of her career as she reached the Dubai Tennis Championships semi-finals, along with Iga Swiatek.

Cirstea was a set and 5-1 down against reigning Wimbledon champion Marketa Vondrousova but recovered to earn a 2-6 7-6 (7-1) 6-2 victory.

Swiatek beat Zheng Qinwen 6-3 6-2 but Coco Gauff was knocked out after losing 2-6 6-4 6-2 to Anna Kalinskaya.

In her match, 33-year-old Romanian Cirstea saved six match points.

"To be honest, at a set and 5-1, I wasn't thinking about winning any more," said Cirstea.

"I was like, at least make it nice for the public, at least make it longer and give them a bit nicer tennis.

"Somehow I managed to get this win and I still don't know how I managed it.

"This has to be the biggest comeback of my career."

Cirstea will play Jasmine Paolini in the semi-finals. The Italian was awarded a walkover win over fourth seed Elena Rybakina, who withdrew from the tournament because of gastrointestinal illness.

World number one Swiatek's win against Australian Open runner-up Zheng sets up a semi-final against qualifier Kalinskaya.

Russian Kalinskaya followed up her victory over Jelena Ostapenko by seeing off US Open champion Gauff.

"I'm super happy about my game here," said Kalinskaya.

"She's a great player, a great fighter. I could feel the tension until the last point so it was very important on my side to stay calm and stay aggressive."

With Gauff, Rybakina and Vondrousova going out, it leaves Swiatek as the only seed remaining in the event.