Just seen on the scoreboard that Grigor Dimitrov coughed up 13 unforced errors and just two winners in that last set.

Grim.

Mackenzie McDonald has gone down the tunnel for a comfort break and is taking his time coming back.

Hi, Grigor Dimitrov. Here's an unappetising bagel for you from the world number 186.

Grigor Dimitrov clocks up his 34th unforced error to let Mackenzie McDonald level the score on his serve at 30-30.

And then comes a double fault. Ouch. Another break point.

It's taken by McDonald. Or rather it's handed to him on a plate as Dimitrov goes well, well wide with a forehand.

Madness.

Make that 4-0 to McDonald! The American youngster is on the charge with a hold to 15.

This is ridiculous.

Consecutive unforced errors from Dimitrov means McDonald earns another break.

This is going to five sets, isn't it?

Get well soon! And Judy - if you need a new crossword partner then give us a shout.

Mackenzie McDonald's come back fighting.

He's broken Grigor Dimitrov at the first opportunity and then held to xx to take a 2-0 lead in the fourth.

This guy is seriously impressing out on the Rod Laver Arena.

The only other match still going on is on Margaret Court, where there's a shoe problem developing between Alexandr Dolgopolov and Matthew Ebden.

Dolgopolov - who is a set up - lost his trainer mid-rally, and then the chair umpire seems to have penalised him for it.

After a whole four minutes of discussions, involving the tournament match supervisor, the set finally continues.

Dologpolov is...well...he's not happy.

A big, big moment for both players.

Mackenzie McDonald offers up two break and set points to Grigor Dimitrov.

A wonderfully delicate volley saves one for the American underdog. But Dimitrov fires a forehand winner to take the set.

He lets out a roar - probably of both relief and excitement.

Another edge ahead from Grigor Dimitrov, who holds to 15.

This is tight.

After going backwards and forwards on deuce in the last couple of games, we now have a hold to love from the American qualifier.

This match has everything going on.

*denotes next server

Image source, Getty Images

Phew, ok. Someone's decided to hold. Grigor Dimitrov pushes ahead.

OK. This match is officially weird.

Mackenzie McDonald is handed three break points after a Grigor Dimitrov double fault.

All three are saved by McDonald hitting wide of the lines.

Dimitrov sneaks the advantage but it held up after McDonald comes out on top in a decent rally.

To deuce. Again.

Break point is wasted by Dimitrov, as we go back to deuce numero three.

Now another break point for the Bulgarian, which he takes his time with a whipped ace past his opponent's left side.

Image source, Getty Images

This is scintillating from Mackenzie McDonald.

Big, overawing serves coupled with mega accurate shots down the line. He's really enjoying himself on the big stage.

But then a few sloppy errors creep in towards the end of the service game, and Dimitrov pulls out a bullet backhand to bring us to deuce from 40-0.

McDonald takes the advantage as Dimitrov slaps the net. McDonald then does the same.

Back to deuce we go.

Grigor Dimitrov is broken!

The Bulgarian challenges the line call on his final shot of the game, but he's already sat down so he knows it's out.

American qualifier Mackenzie McDonald edges ahead.

Image source, Getty Images

My word, I look away for two seconds in search of breakfast snacks and Mackenzie McDonald has two break points! Well, well, well.

The first goes amiss when he powers well over, and then Dimitrov brings us to deuce with a smashing forehand.

The Bulgarian takes the advantage but then pummels miles over the baseline.

Back to deuce.

I don't know much about Mackenzie McDonald but what I do know is the American qualifier can dance.

The 22-year-old pirouettes in some style to knock a backhand winner past third seed Grigor Dimitrov. It was a thing of beauty.

McDonald moves 40-30 ahead on his own serve and goes on to hold after a nifty net exchange with the Bulgarian.

Worth noting that Nick Kyrgios will play Jo Wilfried Tsonga in the third round in Melbourne.

That is going to be a helluva clash.

Kyrgios has described the Frenchman as one of his idols.

We're moving along steadily on Rod Laver Arena.

Is this one going to be a long final match?

The two men are level-pegging in the third set.