Near-silence in New York. The odd clap of the hands, shutters of cameras every time Murray prepares to serve. The Scot berates himself after a double faults, then scoops a backhand long. Two break-back points... 

Do we have a white flag? Or a towel to throw in? Dimitrov had given up before the point was over. Plenty of the crowd vacate their seats. Value for money, this ain't.

Can we call this a virtual match point? Dimitrov not even close to getting a forehand inside the sideline.

Image source, Getty Images

Ivan Lendl is on his feet. Not applauding, but leaning on a wall. Andy Murray looks towards his box, probably as stunned as the rest of us. Yet another Dimitrov double fault, barely getting the ball halfway up the net. Murray doesn't need to scamper, but scamper he does. Dimitrov long. Deuce. 

Dimitrov to try again at the start of the third. No mistakes, now. Another break would probably be terminal.

Tom Heath: Murray is playing with a confidence and arrogance I've not seen before saying you have to beat me and good luck.

Image source, Getty Images

That will do. Dimitrov can't get another one of those canon-ball serves over the fishcatcher. Murray two to the good. It would be an incredible turnaround for the Scot not to reach the last eight.

Every so often, Dimitrov shows signs of cracking the case. Set-point saved by wrong-footing Murray. The thing is, Murray is playing with a touch of genius. Incredible speed to get to a Dimitrov attempted pass when the whole court was free. Volley just as amazing. Another set point...

Andy Murray is serving like Pete Sampras here. Unreturned, ace, unreturned. Two set points...

Image source, Rex Features

Murray can't quite pull off an impossible pass, leaving Dimitrov strutting around like Prince Naseem. Just a hold, Grigor. Murray to serve for a two-set lead.

Dimitrov swings for the fences, saving a couple of set points. Barely a round of applause from the crowd. Just a matter of time, even if the Bulgarian does hold here.

The crowd are humming, almost talking amongst themselves as the one-way tennis becomes little more than a sideshow. Dimitrov, barely able to raise his head, can only watch as a Murray forehand clips the line. Set point... 

Darren Lee: Dimitrov is playing like Murray's sparring partner. Solid but basic hitting to one of the best returners ever. I'm off to bed.

Susan Lawrence: A stroll in the park for Andy! Straight sets, me thinks!!!!

Karen: Sat in the hospital. Being entertain by bbc tennis. Keep going Murray!

It is strangely fascinating to watch Dimitrov go through this torture, which also overshadows just how well Murray has played. Quite superbly, in fact. Corner-seeking forehand, one-two serve-backhand. One game away from a two-set lead.

David Law
Radio 5 live sports extra commentator

The crowd can tell Dimitrov is a good player but he's getting his clock cleaned here. He has his head in his hands and he looks almost ready to burst into tears.

Image source, AP

Double fault, double break restored. Expletives from Dimitrov as he slumps into his chair. Awful stuff.

I never fail to be amazed at how quickly momentum can be reversed, at how rapidly confidence can fill a player like air in a balloon. Or indeed, be deflated. For half a game, Dimitrov looks like Rod Laver. When one goes long for 30-30, he aims a kick at the ball in frustration and makes a clown of himself. Then into the net. Break back point...

The Murray juggernaut is halted, at least for the moment. Some rare looseness in there, ended with a wide backhand. The crowd are behind Dimitrov, solely through the desire to see him make a game of it.    

Finally, a Dimitrov sniff. Again he makes a hash of an overhead, but he belts a second into Central Park. Well caught in the crowd. Break point.