Ahmed: "Andy has been surprisingly more than normal aggressive. Is it maybe he isn't fit enough to take the rallies with Novak?"

Josh Jackman: "That deuce point at 4-4 was absolutely incredible - shame it ended with an unforced error."

Amanda Oliver: "Randomly awake in the middle of the night to listen to the tennis #makeitagoodonemurrary"

At 30-15, Murray puffs out his cheeks and flares the nostrils as if he's preparing for a bullfight. Brilliant returning for 30-30. The pair fetch and retrieve, fetch and retrieve... Djokovic attempts a momentum-changing forehand, but Murray responds like a brick wall and Djokovic loses patience - overclubbing a forehand for break point.

The Serb's serve comes to his rescue for deuce. What follows is a mesmeric 29-shot rally. Neither prepared to crumble, both holding strong. One flamethrower after another, the crowd screams, then they groan, Murray into the tramlines... Djokovic roars... he wildly gesticulates... the crowd erupts. Oh, my giddy aunt. From advantage back to deuce to advantage again. Murray fails to negotiate the barrier and Djokovic scrapes through.

Piers Newbery
BBC Sport at Flushing Meadows

"Just as the sense is taking hold among the local patrons that this is not going to be the epic struggle they had been promised, Murray hauls himself level. His team applaud loudly, with Djokovic prowling a few feet below them. Becker remains unmoved down the other end."

Every point a monumental struggle, a battle of strength and a test of nerve. A flick of the wrist from Djokovic sets him up for a driving backhand volley for 15-30. The pair seem to think they're in the circus and have the crowd in the palms of their, erm, racquets... Djokovic sliding towards the tape for a volley... Murray responding with a volley which kisses the tramline. 30-30. Solid serving from the Scot for one of his more comfortable service games.

Djokovic targeting the Murray backhand with a series of crunching blows and the scampering Murray can take no more, launching a backhand towards the umpire's direction. Applause from Boris Becker. At 30-30, Murray is off target with a return but drags the game to deuce.

Image source, Reuters

Djokovic pulling Murray this way and that from the baseline, but screws a forehand wide to gift the Scot a break point and it's the Serb's concentration which dips, netting, and we're back on serve. Ladies and gentlemen, we're set for an all-nighter.

Four games on the trot for Djokovic and Murray must stop the rot. Oohs from the crowd as Djokovic conjures a brilliant lob from his shoelaces for the opening point. The Scot concedes the first two points, but battles back to 30-30 and a big serve out to the wings eases him to within a point of holding. Murray comes through, and he needed to.

Image source, Reuters

At 30-30, Murray returns with such venom that a stooping Djokovic dribbles a backhand towards the tape. Break point Murray. But an 86mph serve fools Murray, and the Serb volleys his way to deuce. Canny serving from the world number one and he holds firm in a crisis.

The standard is already eye-wateringly high. Fans are already on the edge of their seats. Trainers screeching. Crowd roaring... 18 shots... 19 shots.. 20 shots... Djokovic comes out on top but it's only for 15-15. A second double fault from Murray opens the door for Djokovic and a foolish backhand into the tape presents the Serb with two break points. Murray sprints to the net, the pair fire forehands and volleys back and forth but Djokovic is at his rubber-legged best and gets the better of his friend and rival.

Supernaturally good tennis from both players. Murray continuing to fight fire with fire, sweetly hitting a forehand to haul himself to 30-30. The Briton playing tennis of an incredibly high standard, hitting a jaw-droppingly good forehand down the line for break point.

But he lets Djokovic off the hook with what the Scot himself describes as a "stupid mistake" and then he is wild and wide with a forehand. "WHAT WERE YOU THINKING?" Murray roars. Advantage Djokovic. A screwed backhand from Murray and the Serb holds.

From 30-0 to 30-30 and the New York crowd give out a collective groan as Murray nets when the court was all his. Fierce hitting from the Scot, Murray trading missiles while Djokovic has yet to enter the arms race.

Oh. Should Murray fans begin to worry? He double faults and rubs his shoulder. Momentum swings towards Djokovic as the Briton slaps a backhand into the tape. Break point, but Murray responds with a cool ace down the middle.

Another break point saved, Murray stepping in from the baseline to produce an irretrievable forehand. "Come on," he says. But Djokovic collects his third break point. Brutal hitting from both players during an epic rally, and it's Murray who falters, netting a forehand.

"Please take your seats," says the umpire. "Any seat for now," he adds impatiently, while Djokovic patiently waits to get this match under way.

Oof! First blow to Murray. A thumping return down the line. Murray on his toes, aggressive and intense, Djokovic with an overcooked backhand and the Scot leads 15-30. Djokovic with a wild forehand into the tramlines. Two break points Murray. What a start.

Big first serve from Djokovic chalks off one break point and all traces of an early upset are erased as Murray clumsily nets. To deuce we go. Djokovic yet to reach full boil - netting for a third break point - and the Serb goes long once again. He's broken! Broken, I tell you!

There are more celebrities in Ashe than a Saturday night in Faces nightclub. There's Leonardo DiCaprio, Ryder Cup captain Tom Watson, actor Patrick Stewart. The newly married Brad Pitt, too, apparently. LA must have turned into a ghost town.

After beating Jo-Wilfried Tsonga in straight sets in the fourth round, Murray said he was nearly back to his best. Djokovic is a significant step up from the winsome Frenchman, however. The Serb has yet to drop a set in this tournament.

The players have emerged and the soup bowl of a stadium has filled up for this gladiatorial clash. It's the 21st edition of Murray versus Djokovic. Who will receive the key to the semi-final door?

Piers Newbery
BBC Sport at Flushing Meadows

It's pretty lively on Ashe for the most anticipated match of the tournament so far. To the thumping sound of 1970s Canadian rockers Rush, for some reason, seats are scrambled for, arms laden with drinks and snacks, and quizzical looks follow the appearance of possibly famous people of the big screen. It's a New York night session! And it's a gentle 26C with a light breeze. Perfect.

That's the first course gobbled up. Top marks to the chef so far. Any room for a main course, or is it too difficult to digest such a feast during such unwelcoming hours?

Serena Williams will play Russia's Ekaterina Makarova in the semi-finals. "Honestly, I've had a tough year in the majors so you can never underestimate anyone," says the world number one of her three other fellow semi-finalists. "We're all fighting very hard and we all deserve to be here."

Serena Williams: "I felt she was playing really well (at the start of the first set). I didn't think I was doing too much wrong. I thought 'if she keeps this up then she deserves to win'. I really rely on my serve a lot but if my serve is off I'm able to rely on my groundstrokes. I had a lot of fun today and I'm really happy to have won."

Sharp-shooting from Williams - a crisp forehand onto the line, an unreturnable serve - for a 30-0 lead, but Pennetta reins her in to 30-30. Brutal hitting from the baseline, though, earns Williams a match point and the crowd roar in anticipation. First serve down the 'T', Pennetta nets and Williams does a celebratory twirl at the net.

Image source, Reuters

She was two breaks down in the first set but now Williams is through to the semi-finals and ever closer to an 18th Grand Slam.