Here's the moment Nishikori sealed victory - a slightly underwhelming end to a slightly underwhelming match.

Well, that match didn't last long. Hopefully Andy Murray (world number one, if you didn't know) and Marin Cilic will produce a better contest later.

Join us just before 20:00 GMT for the Scot's opening match of the ATP Tour Finals.

Tim Henman
Former British number one on BBC Two

What went right for Stan Wawrinka? Nothing from the word go. He never found any rhythm with his serve, return of serve or baseline game. He will be disappointed but it is important to focus on the job done by Kei Nishikori. 

He was very clean in every aspect of his game. He was patient from the back of the court and mixed things up. The perfect start for Nishikori.

You know how I suggested Wawrinka might have wanted to hit the West End before rush hour, well he's decided not to speak to the TV types.

I think the shops are open until 10 on Oxford Street, Stan.

Image source, Getty Images

Kei Nishikori, speaking on BBC Two, after his straight-sets win: "Today I was very solid from the first game and very confident. It wasn't easy against Stan because he hits a lot of slice and a variety of shots, but I played a good game today.

On potentially climbing up to world number three: "That is my goal for this week, to win matches and reach number three. I see the opportunity to go up the rankings and I've been playing well so I hope to keep it up."

Colin Fleming
British tennis player on BBC Radio 5 live sports extra

That was not what I expected at the start of this match. I thought this would be a closely fought encounter but Nishikori was as impressive as Wawrinka was poor. 

It's a brilliant start for Nishikori to win in straight sets and he looks well set to have a good run at this tournament.

Colin Fleming
British tennis player on BBC Radio 5 live sports extra

Wawrinka has not shown the desire to really dig in and find his rhythm. He's accepted his fate a little bit.

Andrew Castle
BBC Sport tennis commentator

Image source, Rex Features

Nishikori was superb, Wawrinka certainly was not. A strong performance by Nishikori, his tactics - and their execution - spot on.

Andrew Castle
BBC Sport tennis commentator

Interesting change of tactic by Nishikori with the serve and volley on that final point. The effect was Wawrinka might have taken his eye off the ball a little bit.

It's dropshot o'clock. Nishikori wins the first point of his service game with a delicate effort at the net.

Now it's Wawrinka's turn to challenge - he thinks his opponent's serve is out, but it isn't. You need some NishiEye™ Stan.

Nevertheless, it's 40-30 - a sniff of chance for Stan.

Nishikori messes up his first serve then sends down a slow second and comes to the net which might have surprised his Swiss opponent who launches his return towards the Beavermoon.

Stan must hold to stay in the match.

Image source, BBC Sport

Seriously. Nishikori keeps winning these challenges - has he got some sort of Hawk-Eye technology implanted in his eyes? Andy Murray barely won any at the Paris Masters recently.

Wawrinka isn't having the best of days - it's 40-30 - but he just about holds with an ace.

Colin Fleming
British tennis player on BBC Radio 5 live sports extra

Image source, Rex Features

Wawrinka looks impatient, he's not trying to build the points and he's making even more errors.

Wawrinka's lost his bearings - a 24th unforced error now takes the score to 40-0.

Nishikori fires down his fourth ace. He's won points on 82% of his first serves - dominant.

Tim Henman
Former British number one on BBC Two

Nishikori has taken his opportunities so well. He has won three out of five break points in this match.

Andrew Castle
BBC Sport tennis commentator

Image source, AFP

That is a brutal return of serve. A 120mph serve down the middle and Nishikori just stretched. He had a bit of good fortune for the ball to drop in, but he saw it so well.

Stan doesn't like being sent out wide does he? He looks at ease in his service game but all of sudden it's deuce because of two unforced errors.

You can add another. It's break point again for Nishikori.

A 120mph serve is returned with little control by Nishikori but it loops over Wawrinka and just lands in. Stan left it thinking it would go out.

He's broken again.

There are three fans of Wawrinka in the crowd with T-shirts reading 'Out' 'Stan' and 'Ding' who have just been shown on TV. Neil Buchanan would be proud.

This game is a strange one. Nishikori's serves aren't all that powerful and Wawrinka is looking for the big winner rather than stay in the point - it's not working. 

But now Nishikori isn't getting his serves in. It's deuce.

Have their levels dropped? Not judging by that rally, which Nishikori wins with a scooped shot from the baseline that just lands in. He holds with a good serve.

All about timing eh Kei?

Tim Henman
Former British number one on BBC Two

Wawrinka has got to keep holding his serve, and now he has done that he needs to build scoreboard pressure. He has got to do a better job of returning the Nishikori serve.

Image source, BBC Sport

Wawrinka again - like he did earlier - mistimes a waft of the racquet, this time from the back of the court. He's not feeling it today so far.

Nishikori, on the other hand, is feeling it and senses the negativity. His return is too good for his opponent - it's deuce.

Stan has a plan though. This time he comes out on top in a mini rally, then a good first service bails him out.