PANATHINAIKOS head coach Jesualdo Ferreira fears a summer of change at his club could lead to a Champions League shock against Motherwell after Greece captain Giorgios Karagounis failed to make the trip.
Karagounis, who scored the goal against Russia that sent his country into the Euro 2012 quarter-finals, has not signed a new contract amid protracted negotiations with the cash-strapped club.
The 35-year-old also does not look like featuring in the second leg in Athens next week.
Portuguese Ferreira said: "The contract of Karagounis has ceased and Karagounis for the time being is not a member of the squad."
Another Greece midfielder, Kostas Katsouranis, looks set to start on the substitutes' bench tonight after returning to training just last week following his exertions in Poland and Ukraine.
Former Rangers defender Jean-Alain Boumsong revealed at the weekend he and his team-mates are waiting on overdue wages.
Ferreira says the changes in his squad caused by the cashflow problems make him wary of Well.
He said: "Panathinaikos are the favourite due to its history but both clubs are experiencing change and this change can produce surprises.
"Motherwell is a club with a short story in the Champions League but it's an opportunity for them to make history.
"Panathinaikos reached the final of the European Cup in 1971 and this is why they are favourites.
"But history shows you only have favourites until you reach the pitch and then you have to prove your ability."
Boumsong backed up his manager's wariness.
"We're going to face a very good team, especially as their fans will be behind them," the Frenchman said.
"We have to stick together."
Motherwell are in the Champions League because of the collapse of Rangers, and Boumsong believes the crisis at his former club serves as a warning to the rest of Europe.
"It's a bad surprise what happened, but it's a lesson for everyone that football is not protected from the crisis," he said.
"Hopefully every single team will notice that they have to be careful with their financial situation.
"You can be on top one day and if you don't work hard to stay on top then you will collapse."