Sparta Prague is set to face disciplinary action from the Czech FA.
The club said strikers Vaclav Kadlec and Tomas Pekhart were sick with a virus and were unable to play for the Czech Republic's Under-21 side against the Netherlands, while defender Manuel Pamic was ruled out the senior side's friendly with Croatia due to a knee injury.
But all three of them were spotted playing for the club in a warm-up match against Russian giants Zenit St Petersburg wearing different names on the back of their shirts, according to iDnes.cz.
Pamic was playing as Jakub Podany, Kadlec as Pavel Kaderabek and Pekhart was Martin Abena.
A journalist spotted the error and alerted the Russian club, who published photos from the match on their official website.
Sparta has since issued an apology over the incident.
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