Now Dimitrov has the break point after Kyrgios misjudges the Bulgarian's return, watching it drop just inside the baseline.

A hammer of a serve brings it to deuce. An ace follows for advantage. A fizzing backhand winner comes next for the hold.

Nick Kyrgios is swapping shirts. His wardrobe is like the Simpsons', out comes exactly the same salmon top... incidentally the same as Kyle Edmund has been wearing this tournament.

Remember, the winner of this one meets the British number two in the quarter-final.

Another foot fault called against Kyrgios - he's fuming - "that's not possible, I've not been called foot fault for the last three years, that's twice today".

He's 30-15 up.

Deuce. Kyrgios' slamming forehand catches the top of the net and slightly changes its trajectory, forcing Dimitrov to go long.

But the Bulgarian rallies. "Come on," he screams. And he holds.

Grigor Dimitrov almost meets a powerful Nick Kyrgios return on one knee, and he punches it long.

The Australian wraps a forehand of his own into the net to give his opponent a 30-15 lead, before guiding the next one deep into the corner and out of the third seed's reach - 30-30.

Leon Smith
GB Davis Cup captain on BBC Radio

It's been an unbelievable last 20 minutes. Since Dimitrov served for the set and got the wobbles, he's done really well to get through it. He showed great bravery in the tie-break.

I'm still getting my head around what we've seen. That last return from Kyrgios must have been the hardest return I've ever seen yet Dimitrov got strings on it!

So close from Kyrgios, sending a backhand wide from such an acute angle.

Set point Dimitrov.

And he takes it.

Image source, Reuters

Kyrgios is forced to volley three times as Dimitrov fights to stay in the point, before backpedaling and slapping a crosscourt forehand winner.

But that's a wonderful forehand winner down the line from Dimitrov to follow, and he leads 5-4.

Sturdy stuff from Grigor Dimitrov.

Nick Kyrgios is shouting to himself as he sips on some icy water between points.

The Australian finds a massive backhand winner though, Dimitrov leads 4-3.

Dimitrov manages to engage the Kyrgios serve this time and has the Australian scurrying across court, before darting to the net to finish the point with a volleyed winner.

Kyrgios overcooks a slice on the next point, but Dimitrov can't quite reach it - 3-2 to the third seed.

Image source, EPA

Dimitrov responds with his own brute force. 2-1 to the Bulgarian.

Ace. A thunderous start to the tie-break for Kyrgios, he goes 1-0 up.

Dimitrov holds.

We go to a tie-break...

Punchy stuff from Grigor Dimitrov. He brings the power to the table to soar into a 30-0 lead.

The third seed cracks the tape from a whipped backhand after a ferocious Kyrgios return, though, only for the Australian to then drop a backhand of his own long.

Image source, Reuters

Well, Nick Kyrgios has dusted himself off and is now showcasing some of those big forehand winners again.

He moves into a 40-15 lead, before nailing an ace right on the line.

Leon Smith
GB Davis Cup captain on BBC Radio 5 live sports extra

What a poor game from Dimitrov! He got timid and has left the door wide open for Kyrgios. How he would like to rewind 10 minutes.

Kyrgios will now go up a level, the crowd will get excited again and that's just when it looked like it would be an uphill battle.

Nick Kyrgios is back in this one! The Australian breaks, and the Rod Laver Arena absolutely love that.

Delightful from Nick Kyrgios, and now it's the Australian with a break point.

His first of the match.

Kyrgios saves it, forcing Dimitrov back behind the baseline and the Bulgarian goes long.

Deuce.

Double fault from Dimitrov, live text commentator's curse and all that... if such a thing exists.

But he responds with an 11th ace - 30-15. Kyrgios rolls in a dipping backhand, like a Test bowler mixing things up with a slower delivery, and that throws off the Bulgarian.

His next shot is called long by the umpire. Kyrgios challenges. It is long.

Set point Dimitrov.

Grigor Dimitrov has the chance to serve for the second set.

Nick Kyrgios has been brilliant at times, infuriating from the crowd's point of view at others.

But Dimitrov is equally brilliant, and more consistent right now. He's pretty much silenced the Rod Laver Arena.