David Law
Radio 5 live commentator

I just asked former British number one Jo Durie who's going to win today.

Long exhalation. 

"I think Williams might just edge it. I think she'll be ready for her. But Jo could win. It's that close. That's why it's so much fun."

Image source, Getty Images

You don't need to look beyond the first two shots of the rally to find out where tonight's quarter-final will be won and lost.

The Daily Telegraph's Simon Briggs has crunched the numbers , externalaround serve and return.

And once again, Johanna Konta stacks up pretty well.

"Johanna Konta has the superior percentage of first serves landed: 65 per cent to Serena Williams’s 56 per cent," Briggs writes. 

"As a result, Konta has won an astonishing 94 per cent of her service games. To put that into perspective, the next-best figure is 85 per cent, by Garbine Muguruza, while Williams stands on 82."

Image source, AP

Johanna Konta and Serena Williams will have to go some to match what we have already seen on the Rod Laver Arena already today.

Croatia's Mirjana Lucic-Baroni - ranked 79th in the world - has reached her second Grand Slam semi-final, 18 years after her first as a 17-year-old at Wimbledon 1999, by beating Karolina Pliskova.

Now 34, she has endured a difficult life off the court, fleeing Croatia to Florida as a teenager., external

She delivered a stirring motivational speech after her fourth-round win over Jennifer Brady.

“I will tell it to anyone struggling out there," she said. "Actually, I can’t say it because the TV’s here and I’m going to get fined."

“Oh go for it,” her interviewer said. “Go for it!” 

“F everything and everybody, whoever tells you you can’t do it. Just show up and do it with your heart,”

Leon Smith
Great Britain Davis Cup captain on Radio 5 live

I just walked past the warm-up area and Johanna was there and she smiled and waved, dancing around doing her preparation, she looked in a really good place.

Jill Craybas
Former world number 39 on BBC Radio 5 live

When you play Serena it can be very intimidating, but as well as Konta has been playing, I just don’t get the sense she is intimidated at all.

Russell Fuller
BBC tennis correspondent

Konta's coach Wim Fissette says she has one of the top three serves in the women's game, and that serve has been more effective than Williams' in Melbourne so far.

Williams has had her serve broken seven times; Konta only twice. And the statistics suggest the speed of the world number two's serve drops at crucial moments.

The evidence of the first four rounds can be misleading, though, as Williams tends to raise her game when she knows her title chances are under threat - which they certainly are today.

Image source, Rex Features

Johanna Konta is currently coached by Belgian Wim Fissette, who took on the role from Esteban Carril at the start of this year.  

Fissette said that he first saw Konta play when she took on Victoria Azarenka, a former charge of his.

"I was very impressed with the attitude she had," he says.

"She showed respect to the player but she was there to win the match. She came on the court with the belief that she could beat a top player like her and I still see that.

"I believe there will be a day when she will win a Grand Slam."

The two players stalk through the corridors beneath and behind the scenes of the Rod Laver Arena.

Johanna Konta leads the way, looking cool and composed.

Serena Williams behind her only has one pre-match game face - jumbo-sized earphones clamped around her head, intensity set to 11.

Both emerge into the Melbourne sun and we are ready for a coin toss. Once Serena is done applying a bit of sun cream.

With day 10's high forecast to be a paltry 22C with a light breeze, there should be none of the fainting ball boys or melting water bottles that Melbourne Park has offered up in the past. 

Image source, BBC Sport

BBC Radio 5 live

As you have probably realised, we have text commentary for tonight's big match - but that's not all. 

A click at the top of this page will bring you 5 live commentary, which will be repeated from 07:00 GMT in Tennis Breakfast. You then have time for a significant nap before catching the TV highlights on BBC Two at 16:45.

Image source, Rex

Serena's progress to the last eight has been straightforward.

Four wins, without a set dropped.

But Johanna Konta's has been positively serene.

She has also racked up eight unanswered sets, but dropped only 22 games compared to Serena conceding 27.

She has spent 26 minutes less on court and the average ranking of her opponents has been 43 in the world. Serena's foe averaged out at 57.

Something is going to have to give. 

Image source, Rex

"I've played quite a few Grand Slam champions and former world number ones."

But with all due respect to the likes of Caroline Wozniacki, Svetlana Kuznetsova, Sam Stosur and Venus WIlliams - all of whom Johanna Konta has beaten over the past six months - none are quite like Serena.

Williams is the queen bee of women's tennis, a solo superpower.

Over the past two years, she has reached six of the eight Grand Slam finals, winning four.

The last time she failed to make at least the last four of a Grand Slam was back at the 2014 US Open.

She is a whole different kettle of fish.