An entirely weakened Denmark side, filled mostly with third-division and futsal players, lost 3-0 in Slovakia on Wednesday.
Slovakia, which included leading players like Napoli midfielder Marek Hamsik and former Liverpool defender Martin Skrtel, said before the game that its squad had been harmed by the Danish dispute and asked European football's governing body UEFA to deal with the case, and confer "adequate consequences."
Organizers dropped ticket prices to one euro because of the depleted visiting team.
"It was tough to get motivated for a game like that," Hamsik said.
The home side went ahead when forward Adam Nemec beat Denmark goalkeeper Christoffer Haagh, who is a futsal player, with a header in the 11th minute.
Albert Rusnak made it 2-0 in the 37th minute before substitute Adam Fogt put through his own net with 11 minutes left.
Negotiations collapsed between the Danish footballers' union and the national federation (DBU) over a new collective bargaining agreement regarding commercial rights, and players from the original squad were sent back to their club teams on Monday.
The previous collective bargaining agreement expired on July 31 and the two parties have been unable to agree a new one.
The DBU called the result an "honorable defeat."
It remains to be seen what sort of team Denmark will field in its opening UEFA Nations League game at home to Wales on Sunday.
Slovakia's Erik Pacinda in action with Denmark's Anders Husballe Radovan Stoklasa during their international friendly on September 5. /VCG Photo
Slovakia's Erik Pacinda in action with Denmark's Anders Husballe Radovan Stoklasa during their international friendly on September 5. /VCG Photo
Amazing amateurs
Most of the new squad are on amateur contracts with their local teams. Striker Anders Fonns, 30, sometimes works in a warehouse while goalkeeper Larsen, 23, is a newspaper hawker.
Christian Offenberg, another forward, is a part-time salesman who also plays for Danish third-tier side Avarta and right-back Simon Vollesen, who plays in the Danish fifth tier, is a student
Even Danish Finance Minister Kristian Jensen offered to join the squad. "I report for duty in the nation’s service as a tough right fullback," the minister wrote on Twitter.
Denmark are ninth in the world rankings and reached the last 16 at this year’s World Cup in Russia.
(With input from agencies)