After five hours of typing, I'm going for a lie down.

Make sure you join us back here for day four coverage, starting at midnight.

There's been plenty of drama in Melbourne today.

• Britain's Kyle Edmund won 6-2 6-2 6-4 against Denis Istomin of Uzbekistan to reach the third round for the first time.
• WTA finals winner Caroline Wozniacki came back from two match points down to beat world number 119 Jana Fett.
• Jo-Wilfried Tsonga fought back from 5-2 down in the final set to beat Denis Shapovalov.
• At 15 years old, Marta Kostyuk became the youngest player to reach the third round of a Grand Slam since 1997 as the qualifier beat Olivia Rogowska.
• Jamie Murray made it through in the doubles, as fellow Briton Laura Robson went out.
• Rafael Nadal progressed with another straight-sets victory against Leonardo Mayer.
• Nick Kyrgios beat Viktor Troicki in straight sets to set up a meeting with Tsonga

Head over to our tennis page for more results.

Grigor Dimitrov speaking on court: "What can I say? Tough day. I had to play with what I had and I'm so happy with that. Winning on days when you're not supposed to. He was playing unbelievable and deserves a lot of credit.

"We used to play together back in California and he's improved so much. I had to fight and experience in the end really helped me. And you guys (the crowd).

"I'm so happy with the result and the fight."

McDonald falters.

Match point Dimitrov!

Grigor Dimitrov is eating away at McDonald's service game at 0-30.

But the 22-year-old doesn't panic. In fact, he snatches the power back to level at 30-30.

And then Dimitrov hits the net after doing the splits with an attempted pick-up. He makes amends by placing a backhand out of McDonald's reach.

Deuce.

Grigor Dimitrov nudges ahead again with a hold to 15.

American qualifier Mackenzie McDonald, the world number 186, will serve to stay in the match.

GAME MCDONALD!

No tie-break, remember. We continue...

Dimitrov steals the first point from McDonald's serve.

A lengthy rally ends when the American nets.

But three errors from Dimitrov makes it 40-30.

McDonald thinks he's aced to hold. It's out. Arrrgh.

And then he tries to chip over a drop shot and it fails to clear. DEUCE.

Can't.

Cope.

With.

The.

Tension.

EEK. Double fault for Dimitrov. Not what you need when it's this close in the fifth set.

The third seed watches a couple of loose shots come from McDonald for 40-15, but then he nets a backhand. We're at 40-30.

McDonald nets the next point and Dimitrov holds. This is so tense!

Cooly and calmly, qualifier Mackenzie McDonald brings the score up to 30-0.

A wild shot over the baseline gets Dimitrov off the mark, but then the Bulgarian hits long.

And then McDonald pulls out the money shot to hold - a remarkable pick-up which sails into the corner and overpowers Dimitrov.

McDonald's shank wide pleases Grigor Dimitrov greatly.

But the qualifier responds with a pinpoint forehand on the line, and then finds another clean strike to make it 30-30.

The crowd get REALLY excited (so did I, I screeched) as they think McDonald has somehow stretched and scooped a return ball on to the baseline - but it took a double bounce.

Dimitrov sees out the service game. We go again.

No one is budging. McDonald holds to 15 with confidence.

We're gonna be here for a while yet, guys.

That crowd noise has pumped up Grigor Dimitrov as well.

The Bulgarian holds to edge ahead again in this fifth and final set.

It's getting super late over in Australia now - past 11pm. But the spectators are still up for this, as are the players.

Mcdonald, who remember is an American qualifier, looks like he's cruising to a love hold before he sticks the ball over the white lines, and is then outfoxed by a cross court forehand drive.

The world number 186 stops play and holds his arm up to challenge a call from the umpire. Or rather lack of one. Was Dimitrov's forehand long? Yes, it was. Quite clearly.

McDonald throws his arms up in the air again - this time to try and cajole the crowd along with him as he takes another game.

"Come on now," says Grigor Dimitrov to himself as he plants a juicy forehand down the hard court.

A couple of really decent serves follow and the Bulgarian holds.

Mackenzie McDonald continues to enjoy himself in the Rod Laver Arena.

A sweeping ground stroke fools Dimitrov as the American pushes forward in his service game, which he sees out with a mahoosive ace.

"GRIGOR, GRIGOR," shout the over-enthusiastic Dimitrov crew in the crowd as he moves 30-0 to the good.

He clocks another double fault along the way, but does go on the hold.

McDonald looks like he's going to hold to love, before Dimitrov pulls out a couple of mega strokes to pull the game back.

The American looks relieved when he finally holds.

A brilliant backhand winner gives McDonald a 0-30 lead.

The American qualifier gets down low to try and clear the net on the next point but it doesn't work. 15-30.

He's done the same again so it's 30-30.

Repeat again for 40-30.

Dimitrov holds when McDonald hits a wasteful forehand over the baseline. A let off for the third seed.