Wow. A big backhand down the line creeps inside the baseline to bring Amanda Anisimova back into the game before a double fault levels the game at 30-all.

Anastasia Pavlyuchenkova then fires a shot long to gift Anisimova set point.

Despite serving poorly, Amanda Anisimova races into a 40-0 lead.

Anastasia Pavlyuchenkova, who must be kicking herself for not capitalising on more of these second serves, pegs a point back with a powerful forehand after toying with her opponent on the baseline and a double fault makes it 40-30.

However, Anisimova steadies herself and holds to leave Pavlyuchenkova serving to stay in the set.

Sonia Oxley
BBC Sport at Wimbledon

There are a lot of empty seats on Court One, if anyone has nipped out for a drink they'd better get back soon as this set looks like it might be over pretty quickly.

Annabel Croft
Former British number one on BBC Radio 5 Live

What a match! What an absolutely enthralling contest that was.

I reckon that is one of the most uncomfortable, most painful matches Sabalenka has ever had to play in her life.

Siegemund played that match so well tactically to make her play some of the worst tennis of her career.

Aryna Sabalenka says she will need "some time to cool down and recover" from that quarter-final match. Too right. She was pushed to the limit by Laura Siegemund.

Full quotes to come from the world number one.

Martina Navratilova
Nine-time Wimbledon singles champion on BBC Two

Pavlyuchenkova is not playing her best tennis. She is mis-hitting and mis-timing balls and Anisimova is well in the driving seat.

Pavlyuchenkova is finally on the board but she looks frustrated.

Sam Smith
Former British number one on BBC One

Sabalenka survives.

The toughest of tests for the world number one. I suspect she feels like she has played all four quarter-finals.

I think she might be going head first into the ice bath after that.

I feel like you don't see many lets on second serves but we've already had at least three in this match, including two in a row from Anastasia Pavlyuchenkova.

Amanda Anisimova is continuing to nail her ground strokes, nailing a deep return to set up a forehand winner for 40-30.

However, Pavlyuchenkova keeps her cool to finally get on the board in this quarter-final.

What a drop shot! Laura Siegemund gets the ball just over the net with a swish of her racquet.

Still another break point to save.

Aryna Sabalenka strikes first in a service game that Laura Siegemund must win to stay alive in the tournament. A massive forehand that Siegemund can't get back.

Siegemund still ever so deliberate during her service motion.

The German nets - 0-30. Dangerous times for the 37-year-old. A round of applause from the crowd on Centre Court, trying to raise the underdog for one last effort.

Sabalenka nets for 15-30.

Then Siegemund goes long for 15-40 and two match points for the world number one...

Annabel Croft
Former British number one on BBC Radio 5 Live

This is the most comfortable I've seen Sabalenka in 2 hours and 50 minutes. She is starting to believe she can get through this match.

As in her previous service game, Amanda Anisimova saves a break point and comes through deuce unscathed.

However, she's been far shakier than her 4-0 lead suggests and is really struggling with her first serve.

Amanda Anisimova's ball toss is all over the shop and her head goes down as a double fault leaves her 15-30 down.

Anastasia Pavlyuchenkova hits a forehand return long but is quickly rewarded with a break point as Anisimova finds the net with a poorly struck forehand.

Image source, PA Media

After three breaks of serve in a row, can Aryna Sabalenka hold to nudge herself in front in the deciding set?

Her first ace of the match is quickly followed by a second and a huge scream of celebration.

Over to you, Laura Siegemund - the German will serve to stay in this tournament after the changeover.

Martina Navratilova
Nine-time Wimbledon singles champion on BBC Two

Anisimova has done a great job with her footwork and being in an aggressive position. It is not all arm, your body has to be in the right position as well.

She has one of the fastest second serve return speeds and is doing so well on those points.

Three games into this quarter-final and 13th seed Amanda Anisimova has already converted two of her three break points.

Anastasia Pavlyuchenkova hasn't settled into this game. With a double fault, she's 0-30 down and she's lucky not to find herself facing three break points as Amanda Anisimova easily chases down a heavy-handed drop shot.

However, she can't halt the American for long. Two more break points.

Laura Siegemund goes long! All square again!

More twists and turns than a rollercoaster.

Laura Siegemund goes just wide with a sliced forehand.

Another break point...