Aberdeen have appealed to fans who travelled to Ukraine with them last week to help identify the supporter who has landed them in trouble with UEFA.
The Dons are likely to face a sizeable fine after a flare was set off by one of their followers during their game with Dnipro.
Now Pittodrie chiefs want the person named and shamed - and banned from their games for life.
Operations manager John Morgan said: "We must track down this idiot and stop the club's reputation being damaged any further. Ukrainian officials praised the behaviour of the 500 Dons fans who were at the game but we've all been let down by the actions of one person."
Italian club Lazio were fined £5000 and Romania's Dinamo Bucharest £4000 after fans set off flares before their a Champions Leagueclash in Rome in August.
Both clubs were warned any repeat could lead to their grounds being closed and a ban on fans attending games abroad. The Dons' fate will be decided next month.
Meanwhile, Panathinaikos hitman Dimitris Salpingidis is ready to call on Hearts defender Christos Karipidis to help the Greeks in their UEFA Cup clash against the Pittodrie side.
The striker will ask his countryman, a former team-mate at PAOK Salonika, for a dossier on the Dons who make up Group B along with Atletico Madrid, Lokomotiv Moscow and Copenhagen.
Jimmy Calderwood's take on the Greeks in Athens in the group opener on October 25.
The 26-year-old Salpingidis reckons the draw has been kind because they play the Dons at home - and expects to take all three points.
He said: "I will contact Christos to find out about Aberdeen. We also have Takis Fyssas, who was at Hearts, in our squad so their knowledge will be useful to us. The draw is very good for us regarding the fact three teams will go into the next stage. In front of our home fans I am confident we can win."
Panathinaikos are fourth in the Greek League after four games and trail early leaders AEK Athens by five points.
Midfielder Alexandros Tziolis admits there will be no excuses should they fail to reach the UEFA Cup knockout stages.
However, having learned of how Aberdeen disposed of Dnipro in Ukraine in the first round proper he insists the Greeks will not underestimate them.
He rates Spanish cracks Atletico Madrid as the strongest side in the group but feels his side's European know-how could be vital.
He said "The Spaniards are strong but all the teams can cause problems, especially Aberdeen. But we are an experienced team and that will help us."
