After two routine service games, that was the toughest test yet for Muzza.

He's started this match very calm and collected though, the Scot, none of the chuntering we saw in his opening couple of matches.

Murray battles back with three points on the spin for 40-30 and that should be that...

Wait! Khachanov whacks back a Murray serve with a 91mph forehand winner. He swung at that like a teenager throws him/herself at Swingball when they're playing their older sibling.

A forehand winner gives Murray advantage, but he is pegged back again, before he steps in to put away a forehand winner.

So what do we know about Karen Khachanov? He's Russian, he's 21, he's 6ft 6in and he's the world number 53.

He has already beaten Tomas Berdych and John Isner at Roland Garros this year, and now has his sights trained on Murray.

He also has power. Plenty of power. He hammers down a backhand and then a smash to go 0-30 ahead on Murray's serve...

Image source, Reuters

Brilliant. A backhand drop-shot from Karen Khachanov has more spin than a Shane Warne leg-breaker.

It leaves Murray grunting as he unsuccessfully tries to reach it...15-0.

The pair trade points for 30-15, Khachanov seeing the finishing line when Murray taps a backhand from the baseline into the net.

Murray claws a point back, but Khachanov slams down a hefty second serve that dusts the sideline and beats Muzza all ends up.

Image source, Reuters

Image source, Getty Images

Move on, nothing to see here.

Another easy peasy service game for Andy Murray, who watches a Khachanov return fly back over the baseline to seal it.

Two service games, eight points won, none dropped from the world number one.

Piers Newbery
BBC Sport at Roland Garros

Bright and breezy out on Chatrier, about 20C right now and forecast to get up to 23C. Pretty good for Murray, who's one of the better players in the wind. He also loves a big serve and has great records against the likes of Ivo Karlovic, John Isner and Milos Raonic.

Image source, Reuters

Stephanie Siu: Closest thing I've got to your Parisian café is the charity bake sale we've got on at work. Got a decent brownie. Murray in four!

A bit of early pressure on the Khachanov serve. The young Russian, kitted out in those surfer-style shorts favoured by loads of the blokes at Roland Garros, wallops a baseline forehand long...15-30.

Murray targets his backhand in the next point, but Khachanov digs in to survive after a long rally.

A deep forehand has Muzza scrambling at 30-30, pummeling down an overhead volley for 40-30.

Khachanov groans as he stretches for a forehand on the baseline, Murray moving forward but he can't beat the net with a close-range volley.

Image source, Getty Images

A few early nerves from 21-year-old Khachanov, who is playing in only his third Grand Slam.

This is the first time he has played on this stage. It's like an indie band appearing on the Pyramid Stage at Glasto after only a few gigs.

No such nerves from Murray, of course, the world number one serving out to love with a lovely forehand drop-shot.

Image source, Getty Images

BBC Radio 5 live sports extra

Andy Murray to serve first.

Let's. Play. Ball!

Don't forget you can also listen to the action on BBC Radio 5 live sports extra.

Having struggled with fitness and form during much of the year, Murray played superbly to see off the Argentine in straight sets on Saturday.

"After each round, I'm not thinking about winning," he said.

"I didn't come here with the mindset that I'm definitely going to go a long way.

"I was going to try and just get through the first round and hopefully feel better each day. That's been the case so far."

Top seed Murray, 30, is trying to reach the last eight in Paris for the sixth time in the past seven years.

Khachanov, 21, is ranked 53rd and plays his first Grand Slam last-16 match after beating American John Isner.

"Mentally I feel pretty good just now," Briton Murray said after beating Juan Martin del Potro in round three.

Image source, Reuters

Note to the rest: beware.

Simona Halep is flying.

The third seed shows why she is considered one of the favourites to win the women's singles at Roland Garros with a thumping win against Spanish 21st seed Carla Suarez Navarro.

In fact, she must be THE favourite now.

The Romanian, whose best Grand Slam performance was a defeat in the 2014 final here, batters her opponent in exactly an hour.

Easy money.

Murray's pre-match eating habits won't have been thrown after being summoned to Chatrier quick sharp. But he still might have been surprised to be here so early...

A huge cheer greets Andy Murray as he walks out to Chatrier, a few seconds after his giant Russian opponent.

Muzza has a little plastic lunchbox in his hand. Like one of those you used to take on a school trip. Doubt he has a pack of Quavers and a Penguin* in there though. A few nuts perhaps? Maybe some Djokovic-inspired dates?

* Other cheese-based snacks and milk chocolate bars available

Piers Newbery
BBC Sport at Roland Garros

Once again, it's left to Andy Murray to fly the flag for Britain in the second week of a Grand Slam. He's done a pretty good job of it in the past and was brimming with positivity, relatively speaking, after his win over Juan Martin del Potro. After the rain began to fall on Saturday he was forced to do all his on-camera media wedged into the corner of a hallway in the media centre, with passers by stopping for a gawp. Not much fun, but not a problem.

Image source, BBC Sport

Bonjour mes amies! Apparently it is a bank holiday across the Channel. So, in the spirit, why don't you all tools for a few hours? I think you should.

That means you can spend time with us. We're following every serve, drop-shot and winner as Andy Murray meets Russian world number 53 Karen Khachanov in the last 16.

Grab some croissants, maybe crepes, and a coffee. It'll be like you're kicking back in a Parisian cafe. Almost.

Image source, Reuters

It's easy to let your imagination run wild sometimes. That is a TV programme that will never happen, will it?

Back to reality... Andy is enjoying a relaxing stay in Paris: kicking back on the sofa, watching footy on the telly, spending time with Kim and Sophia.

And, most importantly, winning tennis matches.

At home with the Murrays.

When Sophia is a little older, maybe a teenager looking to forge a showbiz career, when Andy is retired, with a greying thatch and the odd appearance as a 'super-coach', when Kim has relaunched a career as a hard-nosed businesswoman, becoming embroiled in regular public spats with Lady Karren Brady, that might be an idea for a hit reality TV show.

This week, at home with the Murrays, is not so consumer-friendly. Maybe, dare I say it, a little boring. That's exactly how Andy wants it...