John McEnerney: Serena has too much of everything - power, experience - for Vinci, fair play to her for giving Serena a scare but Serena to go through.

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Patrick Mouratoglou is earning his corn in Serena's player's box. He's going through his full repertoire of calming gestures and soothing facial expressions. What a pro.

The tide has suddenly turned back in favour of Vinci though - Serena's being sucked into playing this game at the Italian's slow, staccato pace. A backhand that barely reaches halfway up the net encapsulates Serena's malaise. A return pings off the tape and flops into the tramlines, and Vinci is back level.

Jill Craybas
Former world number 39 on BBC Radio 5 live sports extra

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Drake Watch: the rapper was on his feet after that last game. Meanwhile, down on court, Vinci is not giving in - she claws her way to deuce with a lovely cross-court forehand winner. Serena sends a backhand wide, and suddenly it's break point. And would you believe it, she hands it over with a double fault. That was not what the doctor ordered. Unless the doctor is Italian.

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Jill Craybas
Former world number 39 on BBC Radio 5 live sports extra

Ooh, a few nerves from Vinci as she throws in a double fault. A coruscating return winner from Serena takes her to 15-30, and another big return forces Vinci to net. 

Two break points for Serena. She nets a return on the first, but she plays a superb point at 30-40, finishing the deal with an emphatic drive volley. First blood to Serena in the final set. 

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Jill Craybas
Former world number 39 on BBC Radio 5 live sports extra

Are we one set from one of the biggest upsets in tennis history? Is the Serena Slam about to be derailed by the world number 45? 

Serena to serve first in the final set, which is usually seen a slight advantage. She nets a simple volley on the first point, but she irons out the gremlins and holds to 15.

Piers Newbery
BBC Sport at Flushing Meadows

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The Italian media pack, fresh from the Flavia Pennetta press conference, are not far off rubbing their eyes in disbelief. "You're playing bad," Serena told herself towards the end of that set, before smashing her racquet at the changeover. 

This is not new ground for the world number one, however, as this is the 12th time she has been taken to a final set in her 2015 Grand Slam run. So far, 11-0....

BBC Radio 5 Live Sports Extra

Image source, Reuters

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Williams strikes an early blow, swivelling on a cross-court forehand that beats Vinci. she gets an opportunity on the next point too, but she snatches at the forehand and it finds the net.

Serena then gives the second serve the treatment, swatting it viciously up the line, but her next shot flies over the base line. 30-30.

Vinci has the chance to bring up set point on the next point but she misses the forehand up the line and it's break point. but the Italian battles back, manoeuvring Serena around the court and then firing down an unreturnable serve.

Set point, and she takes it! A superb rally ends with Vinci pinning Serena in the corner and the American firing long. What an outstanding set of strategic tennis from Vinci.

Serena is really battling out there - yelling her approval or displeasure after practically every ball. She seals a comfortable hold to 15 with a big roundhouse forehand. Now, can Roberta Vinci close out the set?

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This is very, very canny tennis from Roberta Vinci - she's making Serena play chess when she wants to do kick-boxing. However, amid the well-constructed points from Vinci, the American is starting to land a few blows, and she brings up a break point with a big forehand.

However, Vinci gets herself out of trouble with a gutsy drop shot, before a wayward return and a wild forehand from Serena give the Italian the game. She's one away from the second set...

No problems for Serena in this service game - she whizzes through a blink-and-you-miss-it hold. Now to attack the Vinci serve...

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Drake's in the crowd today. You know, Drake, the Canadian singer, songwriter, rapper and actor? No? Oh, I give up. Anyway, he's been 'linked' to Serena Williams in the society pages of late, I hear.

His presence isn't doing Serena much good at the moment though - Vinci is more than holding her own with some solid tennis, while the American has really gone off the boil. She nets to allow Vinci to hold to 15.

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Piers Newbery
BBC Sport at Flushing Meadows

"Vinci is now getting sympathetic support from the crowd on Ashe, which is largely here to witness Williams take another step towards greatness, but wouldn't mind seeing her pushed. The stats are inching in the Italian's favour in this second set, crucially the one that says she is now winning 60% of points on the Williams second serve. That just puts the pressure on Williams to make her first. Holding serve will remain a battle for Vinci all afternoon, however."

Perhaps I was a little unfair on Vinci - she's still showing moments of real skill out here, not least at net, where, like compatriot Pennetta, her skills have been honed on the doubles court.

A lovely volley helps her to 0-30, and then a smoking return brings up three break points. Vinci watches two thunderbolts speed past her, followed by anguished cries from Williams, but she gets a look at a second serve and a good return forces Serena to go wide. What a superb game from the Italian - now can she consolidate?

Vinci is essentially relying on donations from Serena: the American is controlling the rallies and it's all about whether she hits or misses with her bludgeoning groundstrokes. The radar is awry in this game, for the most part, allowing Vinci to hold to 30.

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It's oh-so-simple for Serena out there, the serve really clicking into gear now. Aces number seven and eight close out a simple love hold for the American.