It’s the first time in history that the first-team squad will be played at the same time in all four national competitions.
That is because of a rule that the players of the top three leagues in the country will all be in the same squad for the entire season, so there will be no gap between squads for any reason.
The idea was put in place to prevent players from playing in international competitions while on holiday, such as the World Cup.
However, it is now being used as a joke.
Here’s a breakdown of the squads and who is on them.
Roma squad: The only player not on the squad is goalkeeper Gianluigi Buffon, who will be playing in his third European Championship.
He will not be part of the squad because he is not playing for the first team, as he has two internationals in his squad.
The other two are midfielder Simone Zaza and striker Marco Van Basten, both of whom are still awaiting their national team debuts.
It will be interesting to see what happens with Andrea Ranocchia and Leonardo Gama, who are also playing in the competition.
The Italian is due to make his debut in the group stage against Bayern Munich and could become the fourth new face to arrive in the squad, joining Zaza, Gama and Dries Mertens.
Real Madrid squad: This group will be made up of six players.
There are three midfielders, two attackers and a striker.
Gonzalo Higuain and Sergio Ramos will be out of the team because they have not played for the club for a year.
The only other option for Real is winger Javier Mascherano, who is not in the starting line-up for the team against Dortmund.
In addition, Gareth Bale, Cristiano Ronaldo and Mario Gotze are not playing, while Sergio Ramos and Luka Modric are missing due to the World Football Cup.
Juventus squad: Atletico Madrid’s Diego Costa will miss out on the first leg of the competition because of the World Health Organization (WHO) restriction on taking part in international football.
That means he will not play for the Juventus team.
Napoli squad: In addition to the team of Diego Costa, there will also be two other players in this squad.
One of them is forward Diego López, who was born in the town of Alba.
Lózpez has been in the club since 2014 and has also played for Internazionale, Valencia and Atalanta.
Inter squad: Inter’s Matija Nastasic is on the bench for the second leg, while Andrea Belotti, Andrea Pirlo and Marco Verratti are all out.
Borussia Dortmund squad: There will be two different teams in this tournament, one for the Champions League, and one for a third qualifying round.
The Champions League group is composed of five players.
Juventus: Juventus will face Inter in the first round of the tournament, where they are facing Bayern Munich, while Inter will face Manchester City in the second round.
Real: The only other player in the Juventus squad is forward Lucas Perez, who arrived from Juventus last summer for a fee of around €25m.
Manchester City: City will face Bayern Munich in the Champions Leagues second qualifying round, while Manchester United will face Chelsea in the third qualifying.
Barcelona: Barcelona will face Tottenham Hotspur in the Europa League, while Real Madrid will face Atletico in the UEFA Super Cup.