The Champions League showpiece will be held at the Wanda Metropolitano, home to Atletico Madrid, on June 1, with the first Nations League semifinal taking place four days later.
Hosts Portugal are due to appear in that first semifinal on June 5, which is set to be played at the home of FC Porto, with the second semifinal being held 24 hours later in Guimaraes on June 6.
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It means the hosts, as well as fellow Nations League finalists England, Netherlands and Switzerland, could be denied key players in the lead up to those semifinal ties — if they are even called up at all.
England have the highest chance of being adversely affected, with Manchester City (four players) and Liverpool (four players) backed to go far in the Champions League.
Portugal could be without Juventus Cristiano Ronaldo, who did not play in the Nations League group stage, and Joao Cancelo, plus they also have players at Atletico Madrid, Barcleona, Bayern Munich, Borussia Dortmund, Inter Milan, Manchester City and Napoli.
UEFA decided to play the semifinals on June 5 and 6 to ensure they are standalone games, with all other European countries playing in Euro 2020 qualifiers on June 7 and 8. The Nations League third-place playoff and final follow on June 9.
FIFA rules state that players must be released for a major finals tournament 14 days before it begins, but the Nations League is being played on a designated international week in the football calendar and UEFA would not want to devalue the Champions League by enforcing call-ups.
Here, we see how the UEFA Nations League finalists could be affected if their players are in the Champions League final.
Borussia Dortmund: Jadon Sancho Liverpool: Joe Gomez, Trent Alexander-Arnold, Jordan Henderson, Adam Lallana Manchester City: Kyle Walker, John Stones, Fabian Delph, Raheem Sterling Manchester United: Luke Shaw, Jesse Lingard, Marcus Rashford, Phil Jones Tottenham: Eric Dier, Dele Alli, Harry Winks, Harry Kane, Kieran Trippier, Danny Rose
Ajax: Matthijs de Ligt, Daley Blind, Frenkie de Jong, Donny van de Beek Barcelona: Jasper Cillessen Inter Milan: Stefan de Vrij Liverpool: Virgil van Dijk, Georginio Wijnaldum Lyon: Kenny Tete, Memphis Depay Roma: Justin Kluivert
Atletico Madrid: Gelson Martins Barcelona: Nelson Semedo Bayern Munich: Renato Sanches Benfica: Ruben Dias, Pizzi, Rafa Silva, Gedson Fernandes Borussia Dortmund: Raphael Guerreiro Inter Milan: Joao Mario Juventus: Joao Cancelo, Cristiano Ronaldo Lyon: Anthony Lopes Manchester City: Bernardo Silva Napoli: Mario Rui Porto: Danilo Pereira, Sergio Oliveira Valencia: Goncalo Guedes
Benfica: Haris Seferovic Borussia Dortmund: Roman Burki, Marwin Hitz, Manuel Akanji Galatasaray: Eren Derdiyok Hoffenheim: Steven Zuber Liverpool: Xherdan Shaqiri Schalke: Breel Embolo
Starting its journey in 2018 with the doubts that always accompany the new competitions, the UEFA Nations League has been a great success and looks as though it will be around for years to come.
The main objective was, according to the organisers, to ensure that matches between national teams – but not at major championships – had a more competitive edge.
The most important aspect of all is that there are no longer so many stretches of friendlies with little interest for anyone.
Thirty years ago, when there were not so many dates for international matches, the friendlies became more important.
Now they almost serve as a grounding for those who dont play regularly, when in the past it was a matter of pride and prestige to win against another country.
In addition to recovering a competitive nature from the fixtures, this tournament has been a new form of income for national teams.
The four teams that have entered the Final Four will take home between 2.5 to 6 million euros depending on their final position.
But its not only a format that stirs up the aspirations of the big teams, but also those who have the lowest ranking, as it allows for promotion.
Thanks to the Nations League, we have been able to enjoy matches like Spain-England, Croatia-England, Spain-Croatia, Germany-Holland, France-Holland, Italy-Portugal…
Wanting to see big international teams colliding with something at stake will no longer have to mean at least a two-year wait.
A potential negative element and of greater concern to the clubs, is injuries to their best players.
Croatia complained of having fewer days to prepare for their match against England, for example, showing that the combination of friendlies with official clashes has not pleased everyone.
Its worth highlighting too the importance for the team raising the trophy, because as its the first edition, it will be a highly prestigious victory.