I'm baulking slightly as I type this, but this should be excellent. Both players are in form and both will fancy their chances of doing something here. Let's see...

So that's another match in the book - join me again tomorrow when we'll find out who'll play in the other semye-final.

Stephens has really stepped on the gas this afternoon - from about halfway through the first set she's been brilliant, and this is a crushing win over a confident and tricky opponent. She'll play her buddy Maddie next in a repeat of the US Open final and you'd fancy her to win again, though Keys won't play as badly as she did in New York.

Stephens is flowing beautifully now, and while Kasatkina can win points - she takes one with a lovely drop - she can't find a way to dominate. So it is that Stephens rams home the double break and seems certain to finish things off in the next ten or so minutes.

Kasatkina has talent but might not be long for this tournament. She just doesn't have the arsenal to compete with Stephens in this form and now finds herself a set and a break down.

Kasatkina is trying to make Stephens play on the run, but Chris Evert reckons she really needs to seize control of the rallies right from the start if she's to make an impression. Stephens finds really nice angles on the forehand side, and a big one helps her nail the game after Kasatkina rustled up some pressure. The major difference between the players so far has been how well each has played the big points.

Stephens is moving beautifully now, and stroking the ball with severe power - it's great to watch and she's setting challenges entirely different to the repetitive bashing of Wozniack, who Kasatkina beat in the last round. If she can't find away of making Stephens uncomfortable, this will be over very soon.

We're getting to a point where both players are playing well, Stephens threatening Kasatkina's serve and Kasatkina hanging on really well. But despite three chances so to do she can't hold serve because Stephens isn't letting her be, and eventually the break is forced. Stephens will now serve for the set.

Stephens plays a couple of loose points and suddenly there goes her break.Kasatkina is starting to see it now, like she did against Wozniacki.

Stephens is racing away with this. finding great angles from which to pass.Kastakina needs to rouse herself here.

Stephens 3-1 Kasatkina

Kasatkina is only 21 but already she's the Russian number 1 ... the Russian number 1 who has just been broken. Stephens is doing a good job of dominating the centre of the court and looks a class act here; she looks a lot better the girl who beat Wozniacki .

A comfortable hold apiece sees us underway.

Off we go!

Chris Evert reckons Stephens took her foot off the gas once she became a Slam champion and it's hard to argue with. Who wouldn't become precisely that?

Stephens is about to serve...

Out come the players, both looking relaxed and Kasatkina playing her first Slam quarter.