England can take a major step towards the 2026-27 Nations League quarter-finals when they face the Czech Republic at Wembley on Tuesday night.
Thomas Tuchel's side sit second in Group A3 after three matches, with victory putting them on the brink of securing a place in next March's knockout stage.
Tuesday's fixtures will complete the fourth round of group-stage matches, before the final two rounds take place during November's international break.
The top two teams from each of the four League A groups will qualify for the quarter-finals, which begin in March 2027.
Meanwhile, the Nations League also determines promotion and relegation across the lower divisions.
Teams finishing top of their groups in Leagues B and C earn automatic promotion. Second-placed teams in those leagues will face third-placed sides from the division above in promotion/relegation play-offs.
The losers of those play-offs will be relegated, along with teams finishing bottom of their groups in Leagues A and B.
However, the format will change for the next Nations League cycle in 2028 and 2029. All League D teams are therefore guaranteed promotion to League C, while no League C teams will be relegated at the end of the current campaign.
The revamped competition will feature three larger leagues, with League D removed entirely.
Portugal are currently the only team guaranteed a place in the quarter-finals after winning their opening four matches in Group A4.
Spain could join them on Tuesday if they beat Croatia and the Czech Republic fail to defeat England.
Should England and Spain both win, Tuchel's side would need only one point from their final two group matches against Croatia and Spain in November to secure a place in the last eight.
Group A1 remains tightly contested. France and Italy occupy the top two positions, with Belgium just one point behind Italy in third. Two of those three nations will progress.
There is a similar situation in Group A2, where the Netherlands and Greece are three points clear of third-placed Germany. Serbia sit bottom without a point, leaving the current top three battling for two quarter-final places.
Portugal have already qualified from Group A4, while Denmark are second and three points ahead of Wales and Norway. One of those three teams will join Portugal in the knockout stage.
The quarter-finals will be played over two legs during the March international break.
The four winners will advance to the semi-finals in June 2027. Those ties will be decided by single matches on 9 and 10 June, with the final scheduled for 13 June.
England are well positioned in League A, but Wales face a much more difficult route to the quarter-finals.
Wales have collected three points from four matches in a challenging group containing Portugal, Denmark and Norway, with their victory coming in a 2-1 win over Norway in Cardiff.
With Portugal already through, Wales will likely need close to maximum points from their remaining matches against Norway and Portugal to have any realistic chance of reaching the last eight.
Finishing third would send Wales into a relegation play-off in March, while finishing bottom would result in automatic relegation to League B.
Scotland still have three matches remaining and face Slovenia at Hampden Park on Tuesday.
They enter the game third in League B1 but are behind Slovenia only on goal difference. Victory for Sebastien Pocognoli's side would move them into second place behind Switzerland heading into November.
Scotland then face bottom-placed North Macedonia before their final match against Switzerland. Wins in their next two fixtures would put them in a strong position to secure a top-two finish.
Northern Ireland, meanwhile, have enjoyed an impressive campaign. They have recorded two wins and two draws without conceding a goal across their opening four Group B2 matches.
They lead the group by one point, with fixtures against bottom side Ukraine and second-placed Hungary still to come.
Victory over Ukraine, combined with Hungary failing to beat Georgia, would guarantee Northern Ireland top spot and promotion. If both Northern Ireland and Hungary win, their final meeting would become a promotion decider.
The Republic of Ireland sit third in Group B3 after collecting five points from their opening four matches.
Their final two fixtures come against the group's top two sides, Austria and Kosovo.
Winning both would guarantee a top-two finish and could even put Ireland in position to win the group, depending on goal difference and the outcome of Austria's meeting with Israel.
The importance of this Nations League campaign extends beyond promotion, relegation and the knockout stages.
Once the competition is completed, all 54 participating nations will be ranked according to their performances.
Those rankings will directly influence qualification for Euro 2028, which will be staged in England, Scotland, Wales and the Republic of Ireland.
The Nations League standings will also determine seeding for the Euro 2028 qualifying campaign.
Regular qualification will run from March to November 2027, with play-offs for the remaining tournament places scheduled for March 2028.
Unlike traditional host arrangements, none of the four Euro 2028 co-hosts have been granted automatic qualification.
UEFA has instead confirmed that up to two tournament places can be awarded to the highest-ranked co-hosts who fail to qualify through the primary qualification route.
Different play-off scenarios have been created depending on whether zero, one or two co-hosts require those reserved places, meaning either eight or 12 teams could enter the play-offs.
Euro 2028 will feature 24 teams.
Twenty places will initially be filled by the 12 qualifying group winners and the eight best runners-up.
The remaining runners-up will enter the play-offs alongside Nations League group winners from Leagues A, B and C who failed to finish in the top two of their Euro 2028 qualifying groups.
If additional teams are required, the highest-ranked League D group winner will enter the play-offs.
Any remaining vacancies will then pass to the next-highest-ranked teams in the overall Nations League standings until all play-off places have been filled.
That makes the current Nations League campaign particularly significant. Results will not only determine trophies, promotion and relegation, but could ultimately provide nations with another route to Euro 2028.
