Yet more momentum shifts in this set.

Kartal brings up a break point after a couple of errors from Navarro.

Melanie South
Former British Fed Cup player on BBC TV

Navarro won't show it, but she'll be impressed with Kartal. In these situations, you expect a dip. Navarro was probably expecting the break then.

Kartal saves break point then Navarro goes for aggression by coming forward but she can only send her return into the net.

A tough, gritty hold for the Brit.

Navarro has turned things around in this set and brings up a break point on the Kartal serve.

Kartal is having to grind her way through this service game. She sends one long for 30-30 before Navarro goes for aggression and sends it long.

A brilliant rally ends with Navarro chasing down the drop shot then sending the overhead smash down for deuce.

A few unforced errors peppered in that game from Kartal and Navarro takes the hold to love. Gratefully, I'm sure.

A crunching forehand to the corner saves the first break point before Navarro puts the ball on Kartal's toes and the Brit can only send her return long.

There's the break back at the first opportunity.

An extraordinary point ends with Kartal leaving the drop shot but it lands in! She haunches over in disbelief.

Speaking of insane drop shots, Kartal nails one then Navarro produces one of her own to bring up break-back points.

Another unforced error and Kartal has the break of serve at the first opportunity!

Absolutely no sign of letting up from the Brit and Navarro is struggling.

Image source, Getty Images

Well, Kartal carries on in the same vein and immediately brings up break points on the Navarro serve.

The best of the stats from set one.

What a start for Kartal.

Navarro leaves the court for a bathroom break but we're swiftly back under way.

Can the American turn this around?

Olga Savchuk
Ukrainian former player on BBC Red Button

Insane level of tennis from Kartal, she really raised the level higher and higher. Hopefully it will give her confidence for the first few games of the second set which will be so crucial.

Wow wow wow. Sonay Kartal can do no wrong!

She was being dragged all over the court by Emma Navarro but after chasing down a drop shot, she nails the smash to take the first set in style.

Remember, Kartal is yet to lose a BJK Cup match...

My, oh my. Deep behind the baseline and with Emma Navarro closing in on the net, Sonay Kartal pulls out the passing forehand winner for 30-0.

With a big serve, she has three set points.

Momentum swings again! Sonay Kartal has converted all three of her break points.

Great Britain will serve for the first set.

Advantage Kartal. It's another well-constructed point from Kartal but Emma Navarro's forehand lets her down once again.

That's a messy game from Emma Navarro.

Well placed for a routine hold at 30-0, another glut of groundstroke errors let Sonay Kartal back into the game.

Sonay Kartal finds the net with her approach shot. Emma Navarro has broken back!

Whatever Lindsay Davenport said to her at the change of ends has worked wonders. USA are back in this first set.

That's more like it from Emma Navarro! Dragged out wide by Sonay Kartal, she fizzes a running forehand winner back across the net at an acute angle for 15-30.

And then she outlasts Kartal in another brutal baseline rally to earn a break point.