Murray has taken note of those stretches by his opponent.

Is Nishikori tiring? The world number one wants to find out, playing a drop shot on two points in a row.

Nishikori still looks good from the baseline though, firing a forehand down the line. Murray gives an exacerbated look towards his box.

Are we going to see a third break in a row? To deuce we go again.

Feeling confident that Murray will wrap this one up before you start making your dinner? Tennis commentator David Law has a word of warning...

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Here's an opportunity for Murray.

His opponent goes wide with a volley. Break point to the Scot.

He gets it! Nishikori goes wide again.

Murray clenches his fist. Nishikori leans against the backboard to stretch out his calf.

Can Murray get straight back on terms?

He is trying to step into his return and put his opponent on the defensive.

Nishikori finds himself a point away from the game but a hard-hitting point goes Murray's way. Deuce.

Barry Flatman
Sunday Times tennis correspondent on BBC Radio 5 live

There is no pattern to this match. No pattern whatsoever.

Doesn't it worry you that if Murray plays this inconsistently against Wawrinka, what damage the Swiss can do.

Image source, Getty Images

Fair play Kei Nishikori.

After such a poor breaker he could have crumbled but no, he breaks Murray with another well crafted point.

Muzza's thighs get another slap. They'll be red raw if this goes the distance.

Muzza will be looking to ram home his authority here as the Scot starts us off in this fourth set.

Both players throw in a couple of errors but ask Carlos Ramos to get out of his seat and check the mark in the clay. Who knows, the Spaniard might appreciate the chance to stretch his legs.

Murray gives his racquet a hefty whack in the red stuff as Nishikori's forehand gives him an early break point.

Piers Newbery
BBC Sport at Roland Garros

After a tie-break that bad, it's little wonder Nishikori took it out on his racquet. His matches so often produce strange scorelines due in part to his streaks of brilliance, interrupted by some pretty rotten stuff. Murray will still need to tighten things up on serve if he's to close this out relatively comfortably. Meanwhile, Lendl stands for a stretch. He's beaming with satisfaction, on the inside.

Ally Siu: Murray is amazing to be able to switch gears and tactics so quickly!

Russell Fuller
BBC tennis correspondent at Roland Garros

That must have been the worst tie-break I've ever seen put together by a top 10 player.

Can Murray take the tie-break to love? Yes he can!

Nishikori returns into the net and then slams his racquet down in anger. He's livid.

The world number one is in the driving seat.

Image source, AFP

Nishikori is furious. Swinging his racquet against the surface of the clay. How has he thrown away this tie-break?

Murray refuses to give up and runs down a ball he had to right to get. Nishikori makes the mistake again.

As they change ends, Andy Murray has won all six points in this tie-break.

Nishikori's first serve is out. His second serve is good but then he shanks a backhand well over the chalk.

The Japanese is losing his cool here.

Image source, Reuters

Nishikori takes an age mopping his face with his towel before the next point. No movement from umpire Carlos Ramos.

Double fault from the Japanese player! He is crumbling in this tie-break.

Murray adjusts his hat, serves, and takes another point as Nishikori hits long.

This is going well for the Scot.

First serve missed by Murray. Not much in it but it was wide.

Nishikori goes for the jugular, looking for a backhand winner down the line but he nets.

Murray stays ahead.

Tie-break time!

Nishikori waits for the crowd to hush before serving...and then he massively overcooks a forehand and the point goes to Murray.

Murray slaps his legs when he gives Nishikori the first point by playing a drop shot that clips the tape and falls back on the Scot's side.

Murray is ticking. More slaps of the thigh and a scream to his box as falls 0-30 behind.

Another sneer to his box by Murray. Nishikori's coach Michael Chang is on his feet. Nishikori sets up two break points...

And he takes the first of them! The crowd cheer. They want more. To a tie-break we go.

There's the break!

Murray has had one of them already in this set but this time he knows if he holds his next service game, he'll be a set from the semi-final.

Image source, EPA