* Pennetta races through second set in 24 minutes
* Both players struggled with serve early in match (Adds quotes and detail)
By Simon Evans
NEW YORK, Sept 4 (Reuters) - Unseeded Flavia Pennetta never dreamed of being among the last four women standing when the U.S. Open began, but a 6-4 6-1 win over fellow Italian Roberta Vinci on Wednesday put her into her first grand slam semi-final.
After defeat at the quarter-final stage in Flushing Meadows three times before and undergoing wrist surgery a year ago, the 31-year-old Pennetta could have been forgiven for thinking that her chances of a last four spot at this event had passed.
"At the first day of the tournament I never thought I would be here and talking about the semi-final," Pennetta said about her mindset heading into the year's final grand slam.
"I didn't play my best tennis in the last six months, and I just try to keep working and working in the same way every day."
Pennetta, ranked 83rd in the world, will face the winner of Wednesday's night match between Belarussian second seed Victoria Azarenka and Slovakia's Daniela Hantuchova.
In the all-Italian quarter-final, the longtime friends from Puglia put on an energetic display as heat and sunshine returned to Flushing Meadows but they both struggled to hold serve in a first set which saw five combined breaks of serve.
"I think we were both a little tense at the start, neither of us played good tennis" said Pennetta, "There wasn't a lot of fluidity in my play but I think I was able to manage the game better in the end."
It was clear that the close bond between the pair, who have played with and against each other since the age of 10, had an impact on their mental approach to the game.
"It wasn't just tennis out there, it's clear that it was different playing Roberta" said Pennetta who managed to settle in quicker.
Tenth-seed Vinci put up some fine resistance in the first set saving two set points before finally succumbing to Pennetta and the effort seemed to deflate her as she lost the second set in 24 minutes.
Pennetta started the second set with a pair of breaks to grab a 4-0 advantage which she never looked in danger of losing.
Vinci, who lost at the same stage last year, seemed almost unaffected by her defeat and was quickly able to talk of the positives of her tournament.
"It was a great tournament, of course. Last year was a quarter-finalist. At the start there was a lot of pressure," said Vinci, who beat fellow Italians Karin Knapp and Camila Giorgi en route to the last eight.
"This time I lost again in the quarter-final. I know I'm a little bit sad, but if you think about just the tournament, I'm happy, of course" (Editing by Frank Pingue)