Unranked Italian Roberta Vinci reached her first ever grand slam semi-final on Tuesday after 6-3, 5-7, 6-4 victory over Kristina Mladenovic.
"It's an amazing moment for me, it's unbelievable. It's my first semifinal in my career. It was an incredible match, so tight, but I fight a lot,” she told ESPN.
"Kristina played so good and at the end probably both were a little bit tight and a little bit scared about the match, but I'm so happy and I don't have words to say!"
Vinci, who turned professional in 1999, had never previously advanced beyond the fourth round of a grand slam singles tournament, but holds doubles titles at all four events.
The 32-year-old struck early and quickly to open a lead over Mladenovic; breaking the Frenchwoman in the second game and holding her serve for the 6-3 win in just 28 minutes.
She attempted to force the second set along the same path; defending six breakpoints in her first service game before breaking Mladenovic in the third to open a 2-1 lead.
However, the 22-year-old struck back immediately and broke Vinci broke twice as she won the next three games to lead 4-2.
The back and forth battle continued, and Mladenovic allowed Vinci to draw level by losing the next two games. She eventually won 7-5 after scoring her third break of the set in the final game.
Mladenovic carried that impetus into the third set, but this time Vinci proved up to the challenge; defending three breakpoints in the fourth game and later taking a 4-3 lead after converting her fifth breakpoint in game seventh.
Vinci was able to hold her serve in the remaining games to win 6-4, and set a match against either Venus or Serena Williams.
The respective world number 23 and world number one will meet in the next quarter-final match on Wednesday, in what will be their first clash at the US Open since the 2008 tournament which Serena went on to win.
Should she repeat that achievement, Serena will become the first woman to win all four grand slam titles in a calendar year since Steffi Graf did so in 1988.
"It's not easy to play with your sister and Serena has a lot of pressure, I think. I will watch the match but I'm so happy to be in the semifinal, so if I play Serena or Venus, it doesn't matter. I'm so happy right now," Vinci added.