Nw york - Ekaterina Makarova has reached the first Grand Slam semi-final of her career on Wednesday with a 6-4, 6-2 victory over former world number one 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 the 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, slowed earlier this season by injury, was under pressure throughout the second, facing break points in her first two service games before Makarova broke her for a 4-2 edge.
A testy bounce of her racquet earned Azarenka a warning, and the release of tension did little good.
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 number one and five-time champion Williams or 11th-seeded Italian Flavia Pennetta on Friday for a place in the title match.
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 is in her fifth US Open quarter-final, trying to match her semi-final run of last year.
She claimed the biggest title of her career in March at Indian Wells, and Pennetta bristled at the suggestion that 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."
Williams, stung by her Grand Slam failures this year, isn't taking anything for granted.
"I think the older she gets, the better she plays," Williams said of Pennetta -- who like herself is 32.
"We played in Cincinnati. I won. But she played well. This is a new week ... she's going to come out ready to fire and play again."
Williams suffered an injury scare on Tuesday as she and sister Venus were knocked out of the doubles, taking a timeout to have her right foot and ankle taped but appearing unhindered by any discomfort after that.
The other women's semi-final was set on Tuesday, with former world number one 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, joing Li Na and Zheng Jie as the only Chinese to make it so far at a major.