Ekaterina Makarova has reached the first grand slam semi-final of her career with a 6-4 6-2 victory over former world No.1 Victoria Azarenka.

“I’m feeling amazing – finally I’m in a semi-final,” said the Russian left-hander, who had failed in four prior major quarter-finals.

“It’s a great feeling.”

Azarenka, a two-time Australian Open champion who was runner-up to Serena Williams at Flushing Meadows the past two years, gained the first break of Wednesday’s match for a 3-2 lead in the first set.

But Makarova broke back immediately and broke the Belarusian again in the final game to pocket the set.

Azarenka was under pressure throughout the second, facing break points in her first two service games before Makarova broke her for a 4-2 edge.

Makarova broke her fading opponent again in the final game, taking the match when Azarenka fired a forehand wide.

In the immediate aftermath of the tie, Azarenka’s spokesman told reporters that the player had suffered food poisoning and had been vomiting in the run-up to the quarter-final.

Makarova will face either world No.1 and five-time champion Williams or 11th-seeded Italian Flavia Pennetta on Friday for a place in the final.

Williams is trying to become the first woman since Chris Evert in the 1970s to win at least three straight titles at Flushing Meadows.

However, the American has faltered in the year’s first three majors, failing to get out of the fourth round at the Australian Open, French Open or Wimbledon.

Williams has won all five of her career meetings with Pennetta, the most recent a straight-sets win on the hardcourts of Cincinnati where Williams claimed her fifth title of 2014.

Pennetta, who claimed the biggest title of her career in March at Indian Wells, bristled at the suggestion she was virtually destined to lose to Williams – even though she hasn’t taken a set off the American since their first meeting in 2008.

“Of course, she’s better than me,” Pennetta said.

“But I still believe I can beat her.”

The other women’s semi-final was set on Tuesday, with former world No.1 and 2009 runner-up Caroline Wozniacki, the 10th seed, booking a meeting with unseeded Chinese Peng Shuai.

Peng, like Makarova, is in a grand slam semi-final for the first time, joining Li Na and Zheng Jie as the only Chinese to make it so far at a major.