Spain arrive at Wembley on Saturday 26 September as world champions, 10 weeks after beating Argentina 1-0 in New Jersey. England start their campaign against them at 7:45pm, and anyone weighing the England vs Spain odds is pricing a fixture that would once have been an autumn friendly. It is now matchday one of a competition that decides who plays a European final next June, who drops a division, and who gets a second route into Euro 2028.

The Nations League has been running since 2018 and still gets dismissed as a rebranded friendly window. Here is what it actually does.

Four leagues, sorted by strength

The 54 nations taking part are split into Leagues A, B, C and D, ranked by ability. Leagues A, B and C hold 16 teams each, drawn into four groups of four. League D is the smallest at six teams, in two groups of three.

The point of the split is that everyone plays opponents at roughly their own level. England know how that feels from both directions. They were relegated to League B, then won Group B2 in 2024-25 to come straight back up, which is why they are in the top tier facing Spain rather than somewhere quieter.

Six matches in eight weeks

The league phase runs from 24 September to 17 November 2026. Matchdays one to four are compressed into the window between 24 September and 6 October, with the last two played between 12 and 17 November. Teams meet each of the other three in their group home and away, six matches in total. The League D groups of three play four.

England's runs: Spain at home, Czechia away, Croatia away on 3 October behind closed doors under a UEFA sanction, Czechia at home, then Croatia at Wembley and Spain in Spain to finish.

Only League A has a trophy to win

The four League A group winners and the four runners-up go into two-legged quarter-finals on 25 to 30 March 2027. The four winners of those reach the Nations League Finals from 9 to 13 June 2027, a short knockout of semi-finals, a third-place play-off and a final, hosted where possible by one of the qualified nations.

Portugal are the holders. They beat Spain 5-3 on penalties in Munich in June 2025 after a 2-2 draw, becoming the first nation to win the competition twice.

Leagues B, C and D have no trophy at all. Their reward is promotion, which is what shapes almost every match played outside the top tier.

Promotion and relegation does the heavy lifting

Group winners in Leagues B, C and D go up automatically. The bottom side in each League A and League B group goes down automatically, and in League C the two worst fourth-placed teams are relegated.

Everyone else in trouble gets a two-legged play-off in March 2027. League A's third-placed teams face League B's runners-up. League B's third-placed teams face League C's runners-up. League C's two best fourth-placed teams face the League D runners-up. Extra time and penalties settle them if the aggregate is level.

That structure means a group is rarely dead by matchday five. Third place and fourth place are separated by a two-legged tie against a hungry side from the division below.

The Euro 2028 back door

Euro 2028 qualifying proper runs from March to November 2027. There will be 12 groups of four or five teams, and the 12 winners plus the eight best runners-up take 20 of the 24 places at the tournament.

Two more places are held back for the best-ranked host nations that have not already qualified, because England, Scotland, Wales and the Republic of Ireland all have to earn their spot despite staging it. Whatever is left is settled by play-offs in March 2028, contested by the remaining group runners-up and the best-ranked 2026-27 Nations League group winners who missed out. Depending on how many host places get used, that is between two and four tickets across single-leg semi-finals and finals.

So winning a Nations League group in November 2026 buys a safety net 16 months later. Anyone about to bet on a League C group in October is really pricing a Euro 2028 play-off place, which is why those markets move on results that look meaningless from the outside.

What Group A3 is worth to England

England were drawn with Spain, Croatia and Czechia in Brussels on 12 February, arguably the hardest of the four League A groups. Spain hold the World Cup and the European Championships, the latter won in a 2-1 final against England in Berlin. Croatia keep turning up in the last four of tournaments. Czechia came up from League B in the same batch as England.

Two of those four reach a quarter-final and a shot at the June finals. One finishes third and spends March defending its League A place against a League B runner-up. One is relegated.

Spain at Wembley on matchday one sets the tone for all of it. Take something off the world champions and England control their own group. Lose, and the away trip to Spain in November becomes the whole season.