Deep and fizzing from Sloane Stephens. She holds.

It's Johanna Konta to serve for a place in the French Open last four.

*denotes next server.

A leaping ace from Sloane Stephens... Johanna Konta's having a look. She checks the mark but that looks good. Konta clips the line with a backhand that proves too much for the American to make it 40-30.

Great resilience from Sloane Stephens, getting caught at the net but leaping to her right to put strings on Johanna Konta's attempted passing shot - 30-0.

Daniela Hantuchova
Former world number five at Roland Garros

I don't think I've ever seen Konta playing this well.

Her shot selection has been incredible tactically and she has executed it superbly.

Image source, Getty

Roger Federer is knocking on the door once more. But no answer just yet...

Stan Wawrinka saves a fifth break point of the match with naggingly consistent groundstroke depth in his opening service game in the second set, before blasting away from the service oche to get back to the stool on level terms.

Magnificent.

Johanna Konta goes from power to precision with a delightfully weighted drop shot to hold.

She's one game away from the semi-finals...

That's an almost perfect point from Johanna Konta, giving Sloane Stephens the run around like a personal trainer dishing out shuttle runs on the baseline before putting the American out of her misery with a winner.

Another backhand down the line makes it 15 points in a row won on serve for Konta as she takes a 40-0 lead.

Daniela Hantuchova
Former world number five at Roland Garros

It's not done yet because Konta has to serve into the wind next and she might start to feel the nerves the closer she gets.

Sloane Stephens holds, and walks off to towel down and contemplate how to recover that break.

*denotes next server.

Sloane Stephens has settled on her own serve, too, but Johanna Konta has the break.

The American punches her way to 30-0 before the energetic Brit bats down a baseline winner.

Daniela Hantuchova
Former world number five at Roland Garros

Image source, Getty Images

Sloane is talking to her box. She's clearly frustrated. It's like they were expecting one kind of tactic but the match isn't working out like that.

Konta is basically hitting Sloane off the court.

Naomi Cavaday
BBC Radio 5 live tennis commentator at Roland Garros

Konta has gone in a new direction to improve her tennis rather than trying to re-find the game she had when she was number four in the world.

Johanna Konta is absolutely cruising on serve at the minute. She makes it three holds to love in a row.

Lovely from the British number one, working her opponent out wide and then cupping a winner into the space left behind. She follows up with a serve-and-volley for 30-0.

*denotes next server.

Image source, Getty Images

Fifty minutes into the first set, finally the Swiss are split.

And it is the traditional top-dog in the rivalry - Roger Federer - who comes out on top.

Can Stan Wawrinka keep his chin and challenge up?

A bit of breeze blowing across Court Philippe Chatrier now. Sloane Stephens wraps her strings around a forehand winner and then thumps a leaping effort into the clay.

Good, quick hold from the American.

Image source, AFP

That's a fifth ace of the day for the British number one - another love hold.

Johanna Konta, yellow and white lines hatched across her dress like go faster stripes, explodes into another service game with some wrist-rattling efforts before showing soft hands to dink a drop shot narrowly over the tape and bring Sloane Stephens sprinting despairingly into the net - 40-0.

We are into a shoot-out.

This match is looking like a feature-length epic.

Even stevens so far as Wawrinka steals back the mini-break.

Wow. Konta generates some serious racquet speed to leave Stephens stranded on the baseline. But the American creaks through her own gears to take the hold.