A low-key shake of the racquet from Jannik Sinner is about as much as he's given away so far.

He means business today inside this cauldron of Aussie support and reels off four straight points to end James Duckworth's second-set resistance.

A rare off-game from the Australian and you imagine it's going to prove very costly on the evidence so far.

Forehand error from Stan Wawrinka. We go on.

Image source, Getty Images

Arthur Gea holds his racquet to his lips in frustration as what should have been a routine cross-court forehand drifts into the tramlines. A gift of a break point for Stan Wawrinka.

Sorana Cirstea is making a habit of starting her service games well and then allowing Naomi Osaka back in.

As Osaka pulls level at 30-30, Cirstea has a word with the chair umpire and it seems like she's got an issue with the balls as she asks for them to be checked at the end of this game.

The world number 41 then gets back to business and puts away two forehand winners to grab the hold.

Arthur Gea saves another break point. By my count, we're heading for deuce number three.

Stan Wawrinka was all smiles during the pause, joining in with the crowd's antics.

And he's all smiles again as his sliced backhand is returned into the net by Arthur Gea for advantage.

James Duckworth was made to work incredibly hard for his previous game - but just five points later the pressure is back on his serve.

Duckworth celebrated his birthday yesterday, but he isn't being offered any gifts here...

A one-two punch from Stan Wawrinka to force a second deuce. A down-the-line backhand is followed by a huge forehand which Arthur Gea can only return into the net.

Gea looks to have snapped a shoelace so play pauses while the Frenchman fetches a new shoe.

James Duckworth lets out a big cheer as he moves Jannik Sinner around the court before the world number two swings a forehand wide of the mark.

He isn't allowed to escape at the first opportunity, as Sinner slides out wide and squeezes in a return, but Duckworth completes his recovery from three break points down with an ace before swinging a defiant fist through the air in celebration.

Mark Woodforde
17-time Grand Slam doubles champion on BBC Radio 5 Sports Extra and BBC Sounds

We might see it fluctuate from here to the finishing line, both players are perhaps untested in the five-set format.

It has certainly been a while since Stan Wawrinka has been caught in a lengthy five-set match.

The young Frenchman Gea is just trying to stay relaxed, he doesn't want to get too amped up.

The net cord once again comes up trumps as Arthur Gea saves the first break point.

He backs himself at the net for the second and is rewarded with a backhand volley into an open court.

Sorana Cirstea has improved as this match has gone on, but Naomi Osaka just seems like she's able to go through the gears and match the Romanian's level.

And after starting the service game with a stunning backhand winner, she ends it with the same shot to move level at 2-2.

Image source, Getty Images

As the clock ticks towards the four-hour mark, Stan Wawrinka is still bouncing around between points.

Arthur Gea undercooks an approach shot and can only just get a racquet on Wawrinka's forehand pass.

Another powerfully struck forehand, with Gea at full-stretch behind the baseline, brings up two break points for the former champion.

James Duckworth slices the ball away in frustration. The Australian blinks first in a baseline exchange to present Jannik Sinner with three break points and a huge opportunity to take charge of set two.

An ace, backed up by another accurate first serve, gets the Australian back to 30-40, before he slams a backhand down the line for deuce.

Great recovery - and it's well received by the crowd - but there's still work to do here...

"Come on!" yells Naomi Osaka as she breaks back - just like she did in the opener after a shaky start.

She steamrolled her way through the rest of that set, so will she do the same in the second?

Arthur Gea loses his racquet as he sprawls to return a serve down the T and although he manages to grab it, Stan Wawrinka clinically picks off a winner down the forehand side.

With a wide serve followed by a forehand winner into the opposite corner, Wawrinka keeps his nose in front.

A collective groan goes up from the stands on Rod Laver Arena as James Duckworth sees an attempted drop shot just come up short.

It likely would not have made a difference, though, as Jannik Sinner seeks to remind him by crashing in his 10th ace of the contest to hold serve to love.

The longer the rally, the more likely it is to go Arthur Gea's way. As soon as he gets Stan Wawrinka's forehand on the run, he can climb all of the baseline and get on top of points.

Just like at the start of the first set, Naomi Osaka is having a bit of a wobble. Although this time it has a bit more to do with the pace of Sorana Cirstea's groundstrokes.

Two misses open up a 30-0 lead for the Romanian, but she is pulled back after looping a sliced backhand into the net.

Stan Wawrinka misses a forehand at advantage.