Oh no. Kevin Anderson is one hold away from going two set up against third seed Andy Murray.

Murray cruises into a comfortable 40-0 lead, only for Anderson show niftier footwork than Danny Zucko to negate a drop-shot. And that sparks a remarkable comeback.

Another ripper of a forehand from the South African forces deuce. And then a thrilling point - Murray scampering and lunging towards the net - leaves Anderson just one point away from moving a double break up. Another quality forehand does the trick.

Kayley Jay: I turned around for 5 minutes and suddenly Kevin is a set and a break up? Am I in the right universe?

Piers Newbery
BBC Sport at Flushing Meadows

"The last time Murray failed to reach a Grand Slam quarter-final was in 2010, when he lost to Stan Wawrinka in the US Open third round on the same Louis Armstrong court. The Briton will not be panicking just yet, he has plenty of experience of digging himself out of trouble - memorably from 6-3 5-1 down against Marin Cilic on Armstrong in 2012, the year he went on to win the title. Anderson is doing a terrific job of protecting his second serve though, so far keeping Murray at arms length."

No mistake from Anderson at the third time of asking. The 15th seed - aiming to reach a Slam quarter-final for the first time remember - asks questions of the Murray backhand which can't be answered. The Briton can only find the net and Anderson clings onto a potentially-vital hold.

Of course, Murray has already battled back from two sets down in New York this year - against Frenchman Adrian Mannarino. But Kevin Anderson is different kettle of fish.

A roar of encouragement from the Flushing Meadows crowd helps Murray to battle back from 40-15 to 40-40. Any signs of nerves from Anderson? A few.

A dancing Murray is seemingly trying to distract Anderson with some sharp moves as the South African prepares to serve - and it has worked. Anderson's first serve has disintegrated and he can't get over the line, despite teeing up two game points. On we go...

Image source, Getty Images

David Law
BBC Radio 5 live commentator

"Murray has come from two sets down to win tennis matches on eight occasions. It's not advisable to try it against Anderson."

Aidan Williams: No skill Anderson? What a mind numbingly stupid thing to say. I suppose by the same logic Sampras wasn't skilled.

Mr H: Anderson is a tough guy to break, but Murray is racking up too much court time in these early rounds. Doesn't look a contender.

Anderson can hardly miss at the moment, leaving Murray struggling with his returning game. Murray introduces the serve and volley to claw his way back to 15-30, then eases down a steady 78mph second serve for 30-30. The Briton is almost, er, rained on by a bird which deposits on the crystal blue surface - and that seems to bring him some luck....

Jeff Tarango
Former professional tennis player on BBC Radio 5 live sports extra

"He always comes out with six or seven bottles of water. He's finished his first one and the ball kids can't find the rest."

Murray appears to be rattled. At the changeover he has a terse exchange with the umpire, the Briton claiming that he someone has pilfered his water supply....

Neat hold from Anderson as he cruises ahead. The highlight of that game was a 130mph bomb which the 15th seed sends out wide - unstoppable. Murray has few answers at the moment, failing to hit the target with another backhand as Anderson holds to 15.

Murray's coach Jonas Bjorkman looks a little flustered as he watches on from the Armstrong stands. And it is not anything to do with the New York heat. His man's current performance is keeping him sweating. A double fault gifts two break points to Anderson.

Murray digs out the perfect response on the first, smashing down a 129mph ace to stave off the South African.

But then....Anderson pulls out some magic that Paul Daniels would be proud of. An inch-perfect dropshot drifts over Murray's furrowed brow and lands on the baseline.

Any chance of Murray nobbling a morale-boosting break at the first attempt? Nope. The British number one doesn't have his best returning game with him at the moment. Murray does, however, get back to 40-30 before Anderson steps on the gas to force Murray into sending a scrambling backhand into the net.

Image source, USA Today

Murray is wearing the expression of a sulky teenager who has just been told he can't go to the school disco. What a scowl. A swig of water washes away the bad vibes though, and he jumps back to his feet before marching back out onto Armstrong. Anderson to serve first....

* denotes next server

Image source, EPA

Jono: It's difficult to stay awake watching players like Kevin Anderson, so one dimensional. No real skill.

Matt McGladrigan: Multiple break points at 1-2. Gotta take your chances.

Jill Craybas
Former WTA Tour professional

"It depends on Andy's mentality. Can he let that first set go?"

Jeff Tarango
Former professional tennis player on BBC Radio 5 live sports extra

"I feel like we need a 10-minute break, because Andy needs to re-group. Anderson is at the peak of his career, playing so offensively. The way he calmly fist-pumped at the end of the set, his coach didn't move. It's as if they are saying 'this party is just getting started'."

Murray must hold. Simple as that. However, he doesn't.

Anderson keeps his nerve as Murray pins him back by going deep. But the South African digs out a sensational forehand, leaving Murray motionless. Anderson takes the first set!

Image source, USA Today

You can't get a cigarette paper between these two, it might become a night match. Anderson lumbers to the net, picking up a half-volley off his laces to leave Murray scampering in vain. Set point Anderson...

Anderson has two serves for the set - and the first one goes begging. Murray clenches his fist after Anderson slams a forehand into the net.