Andy Townsend
Ex-Republic of Ireland international on BBC Radio 5 live

You can't play for a draw. To start with the mindset and attitude has to be to win the game - if you don't have that then you can create real problems.

John Hartson
Former Wales striker in Cardiff

Wales will want to win the game and take the three points - and finish the campaign better than they started it. They want to continue the momentum they have at the moment and win their fourth straight game.

If the game is level going into the final 10 minutes or so it could be absolutely fascinating. A draw is enough for Wales to finish second, but could mean that they miss out on the play-offs altogether.

So do they then push for a winner and risk losing?

Andy Townsend
Ex-Republic of Ireland international on BBC Radio 5 live

We are in for a great night. In an era where international football has been criticised all of a sudden we have a great game here. It is absolutely winner takes all.

Irish fans haven't had to wait quite so long but it will still be 16 years next summer since their last dance on the global dancefloor. A generation of fans will not have seen Ireland play in the World Cup.

Image source, Getty Images

Roy Keane's rant, Robbie Keane's finish, Mick McCarthy and penalty shoot-out woe. 2002 had it all for the Irish as they were beaten by Spain in the last 16.

Wales have only made it to one World Cup finals.

They were quarter-finalists in Sweden in 1958, losing to a Pele-inspired Brazil after getting through the group with three draws.

Classic.

Image source, Getty Images

Arsenal striker Olivier Giroud has been nominated for Fifa's Puskas Award for his 'scorpion kick' volley against Crystal Palace in January.

The 31-year-old's effort has been shortlisted along with those by Venezuela's Deyna Castellanos and South African keeper Oscarine Masuluke.

A GOALKEEPER SCORING AN OVERHEAD KICK! Come on now!

The winner of the goal of the year will be announced in London on 23 October.

This cannot be good news...

Image source, Getty Images

The line-up is taking shape, slowly but surely.

Russia (hosts), Belgium, England, Germany (holders), Poland, Spain, Brazil, Costa Rica, Egypt, Iran, Japan, Mexico, Nigeria, South Korea, Saudi Arabia.

Tom: What happens if Serbia lose 1-0 and Wales drew 6-6 with ROI?

You're already asking hard questions and it doesn't kick-off for 45 minutes! If that happens, then the table-toppers would be decided on fair play points...

This is where life gets complicated.

There are nine groups, but only eight teams can enter the play-offs. So here is a table of the nine teams currently in second place in each group...

(well, the teams from fourth to ninth anyway)

Image source, BBC Sport

Herein lies a dilemma for Wales. A point tonight will guarantee second place in Group D, but could leave them facing finishing ninth in this table and therefore missing out.

It all obviously depends on a lot of other results. But Wales can save everyone a lot of head scratching with a win. Or a defeat, which would put Ireland into the play-offs!

BBC Radio 5 live

There is full commentary from Cardiff for you to enjoy on 5 live tonight, with build-up from 19:00 BST with Mark Chapman.

Listen within this page. Just press play!

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Wales and the Republic are battling it out but group leaders Serbia are assured of a top-two finish and a win against Georgia tonight would seal top spot.

A draw and even a one-goal defeat could also be enough depending on what happens in the Wales v Ireland game.

All eyes on Cardiff...

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James is all over the Republic's selection policy...

Image source, PA

Wales manager Chris Coleman wants his "golden generation" to forget the past and make more history when they face the Republic of Ireland.

Coleman guided Wales to the semi-finals of Euro 2016 - their first major tournament for 58 years.

And a win tonight could take them to their first World Cup since 1958.

"There is nothing for the players to fear," said Coleman. "I think both teams are going to go for it."

Ian Brown
BBC Radio 5 live in Cardiff

When the World Cup qualifying draw revealed its hand in St Petersburg two summers ago, a blanket finish to European Group D immediately seemed feasible.

And so it has proved with Cardiff preparing to stage its biggest international since that Paul Bodin penalty miss 24 years ago.

Tonight's game has taken on the aura of the ultimate winner-takes-all encounter. But, strangely, the size of the prize remains unknown.

Image source, Getty Images

The minimum reward for the victors will be a play-off berth but a positive result could be enough to take either Wales or the Republic of Ireland directly to the finals in Russia - that's IF Serbia slip up against Georgia.

But what if the Celtic countries slug out a draw? Well, that would be curtains for the Republic and potentially calamitous for Wales depending on Serbia and the result of Ukraine v Croatia in a completely different group.

So events in Cardiff, Belgrade and possibly Kiev will determine who is celebrating tonight.

Pythagoras might be required in the commentary box, but you can definitely hear myself, John Hartson, Andy Townsend and 33,000 voices on Five Live and the BBC Sport App from 19:00 BST.

What would qualifying for the World Cup mean to you?Whether you support Wales, the Republic of Ireland or Northern Ireland we want to know how you're feeling, and where you're following from tonight.

Can you do it? What would it mean if you did make it?

Image source, PA

Get in touch with us on 81111 (UK Only, with a name on) or tweet us at #bbcfootball.

Juliette Ferrington
BBC Radio 5 live in Cardiff

Waiting patiently with the hundreds of Welsh fans for the team coach to arrive I had a chat with some of them.

One told me he was so nervous about tonight that he wouldn’t be able to enjoy until the last minute with Wales winning.

It’s definitely got a tense feeling outside the ground ahead of this winner-take-all Group D encounter but also it’s an event now when Wales play, which it never used to be.

Those who caught a glimpse of their heroes shouted plenty of encouraging words as they entered the ground.