World number two Aryna Sabalenka suffered a surprise straight-set defeat as Romania's Sorana Cirstea earned the biggest win of her career to reach the Miami Open semi-finals.

The unseeded Cirstea will play Petra Kvitova or Ekaterina Alexandrova in her first last four appearance at a WTA Masters 1000 event for nearly 10 years.

"I'm a bit speechless," she admitted.

Speaking in her on-court interview, the world number 74 added: "I came out knowing it would be a really tough match. Aryna hits so hard so I knew I had to hold my ground.

"I'm very happy with my performance today. It's a bit unexpected to be honest."

Cirstea, the only unseeded player to make the last eight of the women's draw, is yet to drop a set in a five-match streak in Miami which has also seen her eliminate world number four Caroline Garcia.

She has shown impressive form at the Sunshine Double, losing out to world number one Iga Swiatek in her first Indian Wells quarter-final earlier this month.

Cirstea's latest statement success took her to a second WTA 1000 semi-final, having finished runner-up to Serena Williams at Toronto in 2013.

Sabalenka, 24, responded after Cirstea broke serve in the opening game of both sets.

But on both occasions it was the Belarusian's opponent who was able to reset, before managing to overcome two break points as Cirstea served for the match - and inflicted just a third defeat on Sabalenka in 23 matches this year.

Wimbledon champion Elena Rybakina, ranked seventh, will meet American world number three Jessica Pegula in the other semi-final, with a new women's champion guaranteed in Miami.

Only Kazakh Rybakina, with 12 wins, has more WTA 1000 main draw matches in 2023 than Cirstea. The Romanian is the first player ranked outside the top 50 to win as many as nine matches at the Sunshine Double in the same year.