Scotland, Ireland and Northern Ireland are among the 16 sides hoping to take a step closer to qualifying for next year’s European championships in the Euro 2020 playoffs on Thursday.
AFP Sport explains how the new format will work and who can claim one of the four remaining places at the rescheduled tournament.
How does it work?
Twenty teams have already book their place at Euro 2020 through qualifying.
The 16 sides in action this week are the best-placed finishers from the inaugural Nations League to have not already qualified.
Split into four sections of four, each path will consist of two semi-finals played on Thursday and one final on November 12.
Who is in the mix?
At least one nation from every tier of the Nations League must qualify. Therefore one of Georgia, Belarus, North Macedonia and Kosovo will reach a major international tournament for the first time as the best teams from League D.
Scotland are aiming to end a 22-year wait to qualify for a tournament as they face Israel at Hampden.
“We knew how big this game was going to be a long time. It has always been in the back of our minds, even previously playing other games this has always been the one that everybody has looked at,” said Scotland midfielder Kenny McLean.
“It is the biggest game we have had in a long time, we know that as players, we know how important is it. It is such a big thing for the country. We are ready.”
Even if Steve Clarke’s men make it through to next month’s final, the spectre of Erling Haaland stands in their way as the winners between Scotland and Israel with face Norway or Serbia.
Borussia Dortmund striker Haaland scored his first international goals last month, including a double in a 5-1 thrashing of Northern Ireland, and leads a talented Norwegian generation also including Real Madrid midfielder Martin Odegaard.
There could be an all-Ireland showdown next month as Northern Ireland travel to Bosnia, while the Republic face Slovakia away.
Surprise quarter-finalists at Euro 2016, Iceland host Romania hoping to set up a final against Bulgaria or Hungary.
Will there be fans?
UEFA announced last week that supporters will be allowed to attend the playoff matches if local authorities permit them to do so, up to a maximum of 30 percent of stadium capacity.
In a statement, UEFA president Aleksander Ceferin said: “27 countries on the continent already allow fans to some extent.
“This decision will allow for a coherent approach on a country-by-country basis and not on a competition-by-competition basis which was sometimes difficult to understand for fans.”
Even in countries where fans are being allowed back, in most cases the numbers remain well below 30 percent of stadium capacity.
For Norway’s clash with Serbia, just 200 fans will be allowed in to the 28,000 capacity Ullevaal Stadion.
Fixtures (1845 GMT unless stated)
Path A: Bulgaria v Hungary, Iceland v Romania
Path B: Bosnia and Herzegovina v Northern Ireland, Slovakia v Republic of Ireland
Path C: Norway v Serbia, Scotland v Israel
Path D: Georgia v Belarus (1600 GMT), North Macedonia v Kosovo