Despite a double fault in that game, Stephens then sends one long with Raducanu wrapping up the game not long after.

Six minutes gone, three games played, Raducanu has won all of them.

Russell Fuller
Tennis correspondent in Melbourne

Sloane looks a bit shell shocked but she can find her gears quite quickly. She is the world no. 67.

Jonathan Jurejko
BBC Sport at Melbourne Park

Stephens looks rusty. Not surprising seeing as she has only played one match since the start of October.

The American has had other things to focus on recently: she married long-term squeeze Jozy Altidore - a footballer who played for English sides Hull City and Sunderland - on New Year's Day.

Fourth seed and last year's semi-finalist Stefanos Tsitsipas is in cruise control in his opening match.

The Greek has just closed out the first set against Mikael Ymer of Sweden with next to no alarm.

A dream start for the Briton as Raducanu gets the break of serve at the first available opportunity.

She didn't lose a set in her US Open adventure and has made a flying start to this tournament.

Raducanu wins the opening six points of the match, before sending a forehand into the net to end the run.

But Stephens then goes long and Raducanu is looking at two break points.

Laura Robson
Former British number one on BBC Radio 5 Live

Emma has come out firing from the first ball.

Sloane made the semi-final back in 2013, I remember that as she beat me in the third round which was tough.

Russell Fuller
Tennis correspondent in Melbourne

She goes from somebody 95% of people in the UK not knowing who she is to going to Wimbledon.

This comes with its own pressure. She hasn't had the time to settle. She has been thrown in at the deep end. We will see how she copes with that.

A backhand from Sloane Stephens, in her first game of her first match of 2022, falls into the net and Raducanu is up and running with a comfortable hold to get us going.

Jonathan Jurejko
BBC Sport at Melbourne Park

Emma Raducanu's ascent to superstardom has been so swift, sharp and stunning that the story would be dismissed as fantasy if it wasn't still fresh in the memory.

Winning the US Open as an 18-year-old qualifier without dropping a set - in only her fourth senior tournament - has brought fame and scrutiny the Briton would have never imagined six months ago.

The lens of the world will focus on Raducanu when she starts her Australian Open campaign on Tuesday as the sport's latest female major champion.

It is easy for some to forget - particularly mainstream sports fans whose skewed expectations may demand similar success - that Raducanu is starting her first full season on the WTA Tour.

• Read more of the feature on Raducanu here

Raducanu to serve first and sends a down-the-line winner instantly.

Laura Robson
Former British number one on BBC Radio 5 Live

Weirdly enough the closest parallel [to Raducanu's US Open win] I can think of was Sloane winning the US Open in 2017. She came out of nowhere.

They both had a fantastic US Open albeit different years. I can see some similarities there.

Emma Raducanu is now up to 18th in the world after being at 150th before the US Open, which she then went on to win.

How will she cope with now being the favourite in matches? It's a tough task for her today with Sloane Stephens, who won the US Open in her home country in 2017, on the other side of the court.

Stephens, who has been as high as third in the world rankings, is now down in 68th.

Jonathan Jurejko
BBC Sport at Melbourne Park

It is easy for some to forget that Emma Raducanu is still a newbie.

Raducanu, who turned 19 in November, is playing in the Australian Open seniors for the first time, although she did play two years ago in the juniors.

Last year she was holed up at home in her bedroom, studying for her impending A-Levels.

In her first major since winning the US Open, Raducanu says she is trying to dampen expectation - both internally and from the outside.

"I appreciate all the support I've been given and I'm very grateful. It is a journey, I need to learn to be patient and need patience from those watching," she told BBC Sport at Melbourne Park.

"I need a little bit of space to learn to develop myself and figure out what works. I am just starting out."

It's a late one for the players as the time in Melbourne is 10.05pm, so this one could well go into Wednesday.

Don't forget to send us your thoughts on all the action, by using #bbctennis on Twitter.

Laura Robson
Former British number one on BBC Radio 5 Live

I've watched a lot of tennis today. The women's game is in a really good place and I need a coffee. We will get through it.

We've had a busy week but this for me is the blockbuster of today.

Jonathan Jurejko
BBC Sport at Melbourne Park

Image source, BBC Sport

Seeing a photo of yourself flashing up on a giant billboard must be an odd experience.

Emma Raducanu memorably posed in front of one in Manhattan after her US Open win, but she is not taking centre stage yet in Melbourne's central business district as far as I have seen so far.

That honour obviously goes to world number one Ashleigh Barty, who is aiming to end Australia's 44-year wait for a home champion.

A promo on another screen at the intersection of Swanston Street and Bourke Street - two of the city centre's busiest streets and in the shopping hub - is also led by Barty.

Alongside her feature Greek pair Stefanos Tsitsipas and Maria Sakkari. That's a nod to the huge Greek population which lives in Melbourne.

Image source, BBC Sport

We have live commentary on BBC Radio 5 Live right now so press the play button at the top to listen along.