A bit too much oomph on that forehand from Angelique Kerber, and Maria Sharapova saves the first of three break points.

Sharapova takes an age to serve, spending so much time composing herself, but it's no use as she spears a return wide. Double break for Kerber!

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

This has been a really impressive start from Kerber. I think she has really surprised Sharapova at the start of this match. Sharapova will have to start thinking about plan B.

A roar from the Rod Laver Arena as Angelique Kerber smashes a forehand cross court, sending Maria Sharapova the wrong way.

Once again, three break points come the German's way...

What a weird rally. Maria Sharapova tries a drop shot and Angelique Kerber chases it down, before Sharapova tries to launch into Kerber's smash and skews her shot out.

A fine, fizzing return from Kerber takes her to 40-0 but she double faults.

That's magnificent, though - Kerber charges to chase down yet another drop shot and slices a backhand behind Sharapova, before letting out a yell of "come on!"

* denotes next server

The Serbian flags are waving in the stands. After 40 minutes, Novak Djokovic has this first set wrapped up.

He marches to his seat and then shows off his impressive flexibility by lifting one foot up onto the other thigh and bending over so his nose goes beyond the raised shin. It's making me wince just watching that.

Classic Novak Djokovic.

In danger in his previous game but he wriggles free and then pounces with a break of his own in the following game. The six-time champ races to 0-40 before Ramos-Vinolas fights back to deuce but Djokovic has too much a couple of points later.

The first break of the match in the bag and he quickly wraps up another service game moments later. Novak on the brink of this first set.

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

Sharapova has to serve very well and get the first strike on her forehand. It is such a big weapon. She has to play more points on her own terms. In the first few games she has been the one running.

That's a good serve from Maria Sharapova, and Angelique Kerber can't get her response over the net.

A hold for Sharapova, but it's not been easy.

Wide goes Angelique Kerber with a forehand, and she's annoyed with herself. Not as annoyed as Sharapova, though, as a tame forehand finds the net.

Ooh, and again, Sharapova nets, with Kerber returning deeply. A net cord saves the break point for Sharapova, though. Deuce number three...

Ooft. Angelique Kerber races around a tennis court like a sprinter running the 100m.

She gets to a backhand and forces a winner, before Maria Sharapova shows off some fine forehands of her own for 40-30.

That'll be deuce, though, as Sharapova's backhand sails over the baseline.

Superb striking from this pair but it's Angelique Kerber who comes out on top, coming up to the net and popping a backhand over.

Sharapova responds with a fine forehand winner for 40-15, but Kerber smacks a serve down the T to hold.

Another testing service game for Novak Djokovic with Andre Agassi watching on from the coaching box.

Ramos-Vinolas hammers down a few groundstrokes and then Djoko goes long with a forehand. All of a sudden the Serb is facing another break point.

Once again Djokovic bats away the danger but he still doesn't look too happy. A shake of the head despite one of his trademark backhands landing plumb on the line.

Nice. Maria Sharapova saves the first with a good serve that Angelique Kerber flaps into the net.

That's long, though! An early break for Kerber.

A big serve from Sharapova first up but Kerber is equal to it, firing a backhand return, and Sharapova nets.

Hello, here's three break points! Superb hitting from Kerber, getting Sharapova on the run. Can she capitalise?

Ready?

It'll be Sharapova to serve first.

Kerber has had the best of her recent meetings with Sharapova.

She's come out on top in their last two matches - they haven't met at a Slam since 2014, when Kerber won their Wimbledon meeting 7-6 (7-4) 4-6 6-4.

Sharapova has looked in good touch so far in Melbourne, and she leads their head to head record 4-3.

She beat Tatjana Maria in the first round before overcoming Anastasija Sevastova, who knocked her out of the US Open last year.

Image source, Getty Images

Here come Maria Sharapova and Angelique Kerber.

There's a healthy round of applause for both players as they make their way out on to court.

It's not quite coming together for Juan Martin del Potro at the moment.

Tomas Berdych has broken him at the first opportunity in the second set.

Albert Ramos-Vinolas isn't letting Djokovic have an easy time of it - he's just snared a break point against the former number one.

A hustle up to the net from Djokovic draws the error out of his opponent to force deuce, and a sublime backhand slice allows him to hold.