Unseeded and unsung Sorana Cirstea notched perhaps the biggest victory of her career on Wednesday when she upset second-seeded Aryna Sabalenka 6-4, 6-4 to reach the semifinals of the Miami Open.

It marks the first time Cirstea has reached a semifinal since 2013. On that occasion, she eventually lost to Serena Williams in the final at Toronto.

Cirstea, a Romanian who turns 33 next month, had just nine unforced errors during the victory. Sabalenka, who is No. 2 in the world, is the highest-ranked player Cirstea has ever beaten.

"I think I've always had the game," Cirstea said. "I was always dangerous. But, now and then, I could be a bit erratic. Against the top players, you are not allowed to do that."

Cirstea has won nine of her last 10 matches, including five straight in Miami. Her lone loss during the hot streak was to World No. 1 Iga Swiatek in the Indian Wells quarterfinals earlier this month.

Cirstea defeated World No. 4 Caroline Garcia in both tournaments.

She needed just 85 minutes to finish off Sabalenka, who won the Australian Open two months ago.

"I am a bit speechless," said Cirstea, ranked 74th in the world and owner of just two WTA singles titles since turning pro in 2006. "I came out knowing that it was going to be a really tough match.

"Aryna hits so hard, so I knew I had to hold my ground and I am very, very happy with my performance today and it's a bit unexpected to be honest."

Cirstea and Sabalanka each recorded seven aces during their first head-to-head matchup. But Sabalenka of Belarus committed six double faults to Cirstea's two.

Cirstea will face either 15th-seeded Petra Kvitova of the Czech Republic or 18th-seeded Ekaterina Alexandrova of Russia in the semis. Those two women play their quarterfinal match on Wednesday night.