US Open 2015: Can Serena Williams crack the Vinci code to make final?

New York: Roberta Vinci is confident and care-free approaching her first Grand Slam semi-final, even though it's a US Open showdown Thursday with history-chasing Serena Williams, whom the Italian has never beaten.

"I'm really happy," Vinci said. "I have nothing to lose. Just play my game, enjoy my match and we will see."

The world number 43 Vinci downed France's 40th-ranked Kristina Mladenovic 6-3, 5-7, 6-4, Tuesday to finally crack a Slam last-eight in her 44th try. (Photo: AP)

But she is 0-4 all-time against Serena, who holds all four major trophies and who moved two wins from completing the first calendar Grand Slam since Steffi Graf in 1988 by defeating her sister Venus 6-2, 1-6, 6-3.

Serena can also match Graf's career Open Era record of 22 singles titles, two shy of Australian Margaret Court's all-time mark, but first she has to get past Vinci.

"It's not easy to play her, but we will see," Vinci said.

"I have a lot of experience, but when you play against Serena, it doesn't matter. You have to play better, then better, then better.

"I have to play my game, aggressive, nothing special. I know I have a lot of experience, but maybe against (Serena) I don't need this experience."

Vinci, 32, became the lowest-ranked Slam semi-finalist since 83rd-rated compatriot Flavia Pennetta at the 2013 US Open.

Her nine career titles are 60 fewer than Serena.

"She's the number one. She's an incredible player," Vinci said. "I played against her in Toronto three weeks ago. The serve, it's incredible. It's tough to return. She's the number one."

Vinci was surprised as her quarter of the draw opened up even before the tournament began with Russian third seed Maria Sharapova withdrawing due to an injury.

Exits by Spanish 10th seed Carla Suarez Navarro and Serbian 21st seed Jelena Jankovic one match before they would have played Vinci helped. Serb seventh seed Ana Ivanovic lost in the first round.

And Canada's Eugenie Bouchard slipped and fell in the locker room, sustaining a concussion that allowed Vinci to advance by walkover and enjoy extra rest ahead of the match against Mladenovic.

"When you play the Grand Slams, it's always tough and you have a lot of pressure," Vinci said. "But I think I have also good draw, because Suarez lost, Jankovic the same, Bouchard. So maybe this was my tournament. I don't know. Sometimes it can happen."

It comes near the end of a career that has seen its greatest success in doubles, including 110 weeks as the world doubles number one.

"It's nice. I'm 32. I'm not young," Vinci said. "I'm at the end of my career, so my first semi-final, it's incredible.

"When you work hard for a long time and every single day, sometimes you have some periods down and try to come back. It's not always easy. I'm very proud of myself."

Vinci is taking more chances and firing more winners.

"I'm starting to play much better, more aggressive," Vinci said.

"Also my body is OK. I don't have injury. Maybe now I'm more solid and more in confidence. When you win a lot of matches you are a little bit of in confidence. Is nice when you have this sensation."