The umpire is down out of his seat for a private chat with Monfils. The Frenchman is covering his mouth with a towel, so no idea what they're talking about.

Image source, Getty Images

Leon Smith
Great Britain Davis Cup captain on Radio 5 live sports extra

I think Nadal is hitting it harder, going after the shot a lot more. This looks like a Nadal that is more dangerous than recently.

Well. When the showy stuff comes off - it's great fun.

Monfils hits a snazzy backhand chop slice, while seemingly looking away from the ball, and it drops over the net and he follows it up with a perfect lob.

The crowd lap it up.

Speaking of backhands, Rafa's is looking more potent than is traditionally blockbuster forehand right now.

Nadal, looking like he's nipped into the shower with the sweat running off his face, has two set points but only needs one as Monfils spoons wide.

Image source, AFP

Monfils has had a nightmare with this smash attempt - not only putting it into the net but tweaking his back while he was it.

Not a great slam dunk from the man who likes his basketball.

Oh what's he trying to do? Looking for a through the legs shot in mid-court - he ends up looking stupid and a set point down.

Rafa hits the net to go to deuce, goes long for Monfils advantage and then watches an ace fly by.

A let off for the showman.

Image source, Reuters

Dave Gibbons: Too many unforced errors by Monfils so far. Giving first set to Nadal

A blistering crosscourt backhand from Monfils shows he has the ammunition to take down the Spaniard.

But a forehand into the net shows he can flag deep into rallies.

A long return gives Nadal the game - one away from the opening set.

Image source, AFP/Getty

A lady in the crowd holds up a sign saying "Rafa, meet me in Majorca, puh-lease".

Let him get this Grand Slam out of the way first, eh?

The umpire gets to turn on smug mode as he overrules a Monfils forehand to say it's out - Monfils challenges but the man in the chair gets it right.

The Frenchman comes through, just about, after being taken to five deuces.

Image source, EPA

Third seed Milos Raonic, the top seed left in the men's singles, is through to the quarter-finals after beating Roberto Bautista Agut in four sets.

The Canadian will face Rafael Nadal next. Or Gael Monfils, should he recover to beat the Spaniard.

Nadal has Monfils pinned way beyond the baseline, giving Rafa an age to pick out the ball.

It's also got Monfils' calibration out of kilter as he puts into the net twice.

Rafa's moving nicely along the back of the court - so much spring and bounce - and it's a love hold.

Image source, EPA

Monfils calls for some tape for his fingers - he seems to be put off by a sweaty racquet handle.

Less sweat, more swipe from the Frenchman as he slips a slinky forehand winner down the line.

It's the first love hold of the match and he's on the board.

Image source, AFP

Nadal smells blood.

Monfils sits a backhand up and Nadal sees it all the way, crashing down a backhand winner with purpose.

It sets the tone and Monfils is three down.

Image source, EPA

Third seed Milos Raonic, the top seed left in the tournament, is marching towards victory in the fourth set.

Nadal crashes a forehand volley into the net - a sign on the newer, rustier Spaniard there.

Monfils, equally, could do with the WD40 as he squeaks a wild forehand long for a break point and then double faults to gift wrap the break.

Image source, EPA

You might want to get comfy. If the first game is anything to go by, there will be plenty of rallies.

Fun, juicy rallies.

Nadal has to save an early break point and does so by whipping Monfils around the baseline and stepping in to volley.

And Monfils puts a return into the net to complete a seven-minute game.

Image source, Getty Images

After years of being a perfectly adequate top-20 player, Gael Monfils has turned himself into a more than capable top-10 player.

The world number six is banging on the door of the top five, and a first Grand Slam final appearance would certainly boost those prospects.

The Frenchman reached the quarter-final here last year, for his best Melbourne performance, and has reached the semis at Roland Garros and Flushing Meadows.

Leon Smith
Great Britain Davis Cup captain on Radio 5 live sports extra

It's definitely possible as they're both playing well, but there's other good players in the draw. Federer's playing really efficiently and got bags of confidence.

Image source, Rex Features

Rafael Nadal's last Grand Slam title? The 2014 French Open.

His last Grand Slam quarter-final? The 2015 French Open?

Last time he was ranked as low as ninth in the world? August 2015.

But you won't be writing him off today... here we go.

Image source, Reuters

Croatia's Mirjana Lucic-Baroni ended an 18-year wait for a Grand Slam quarter-final place with victory over American qualifier Jennifer Brady at the Australian Open.

Lucic-Baroni, 34, won 6-4 6-2 to reach the last eight of a major for the first time since Wimbledon in 1999, when she lost to Steffi Graf in the semi-finals.

She will play fifth seed Karolina Pliskova, who overcame the last-remaining Aussie Daria Gavrilova 6-3 6-3.

"I am a tough little cookie and really stubborn," said Lucic-Baroni.

"When I want something I will work hard and do anything I need to get it. What a satisfaction."

Read more here.

Image source, EPA

With the top and second seeds already out of the men's draw, how's the number three getting on over at the Hisense Arena?

Canadian Milos Raonic is taking on 13th seed Roberto Bautista Agut and is having a right ding-dong battle.

Level at one set each, Raonic saved numerous break points at 4-4 in the third and has just gone on to take it 6-4 to go 2-1 up.

The winner faces Nadal or Monfils in the quarters.

"The game is there. It’s all about the head now.

"It’s a big ask when you’ve never played Serena Williams to beat her at a Grand Slam quarter-final but you never know. She’s got the game to beat anyone.

"She needs to follow her game plan, believe in it and commit on every shot. If you have doubts then Serena eats you alive."