Celtic has been reinstated to the Champions League playoffs after qualifying-round opponent Legia Warsaw was punished for fielding an ineligible player as a late substitute.
Legia official Dominik Ebebenge said the club will appeal, and blamed human error for failing to register the player in question for previous qualifying games — meaning those didn't count toward his three-game suspension.
"The proportion between the error and the consequences is unimaginable," Ebebenge told reporters after getting the UEFA verdict one hour before Friday's playoffs draw. "The spirits of the players are broken."
The UEFA decision could potentially cost the club millions of euros (dollars) in prize money for reaching the lucrative Champions League group stage.
Legia won the third-round qualifying match 6-1 on aggregate after following up a 4-1 victory in the first leg with a 2-0 win at Murrayfield on Wednesday.
But the Polish side brought on Bartosz Bereszynski as an 86th-minute substitute in the second leg, even though he was suspended for the game.
Because Bereszynski was not registered for the previous qualifying round matches, he had not technically served the first two matches of a three-match ban for being sent off in a Europa League match last December.
UEFA said in a statement Friday that "the match has been declared as forfeit."
Celtic was awarded a 3-0 victory for the second leg, meaning the Scottish champion advances on away goals, with the aggregate score at 4-4.
"I think the pitch showed who is the better team," Ebebenge said.
Legia will be demoted to the second-tier Europa League playoffs draw Friday.
"Financially, it is a disaster for the club," Ebebenge said. "This is absolutely against fair play and the spirit of the game."
It is the second time in four seasons that Celtic has been reinstated in a UEFA competition because of an opponent's legal problems.
In 2011, Sion of Switzerland was kicked out of the Europa League after fielding ineligible players in its victory over Celtic.