Wales host Hungary in a winner-takes-all clash at Cardiff City Stadium tonight.
And the Euro 2020 qualifying picture is simple for Ryan Giggs' side as far as the game in South Wales is concerned.
If Wales win against Hungary, they will qualify for Euro 2020 automatically.
If Wales draw or lose to Hungary, they will fail to qualify for Euro 2020 automatically, although they will go into the play-offs, which gives them a second shot at reaching next year's tournament.
Giggs will obviously hope to qualify automatically by beating the Hungarians, but here's how the Nations League play-offs could rescue them if that doesn't happen.
How do the play-offs work?
Each of the four Nations League pathways will have their own route to the finals.
There will be four teams in each play-off structure for leagues A, B, C and D, with one from each progressing to next year's tournament.
The play-offs will be two one-off matches, consisting of a semi-final and then a final.
The best ranked team in each league will be at home to the worst ranked side in the same league, while the second best ranked team will host the third best ranked nation.
The host of the final will be decided by a draw.
So who will Wales play in the Nations League play-offs?
This part is somewhat is complicated but, as things stand, Wales will play either Bulgaria, Israel, Slovakia or Republic of Ireland in the play-off semi-final. The good news is Wales will be at home for that one-off game.
They would then play a play-off final, either home or away. This could possibly be against the likes of Bosnia & Herzegovina, Northern Ireland, Iceland, Romania or one of the teams already named. It's a complex formula and it will all come out in the wash tonight.
When are the play-offs?
The play-offs take place in March next year.
The semi-finals will be on Thursday, March 26 while the finals will be held five days later on Tuesday, March 31.
When is the draw for the play-offs?
The draw takes place at 11am on Friday, November 22 after all of the regular qualifying fixtures have been completed.
What about the Euro 2020 draw?
If Wales qualify automatically, they will be in the hat for the Euro 2020 draw which takes place on Saturday, November 30.
(All information correct at time of publishing)
