Schalke defender Kyriakos Papadopoulos has warned his side they will face a "lively battle" against Olympiakos in the Champions League on Tuesday night.
Papadopoulos, 20, said the outcome of the Group A match between two sides who are unbeaten in domestic football so far was difficult to call, adding: "I can't make any predictions."
The Greece international made his breakthrough at Olympiakos, with his first-team debut coming at the age of only 15 in 2007.
His former employers have not lost a European match at home to a German team for 30 years, and defeated Borussia Dortmund 3-1 in the Champions League last season.
But Schalke's Dutch star Klaas-Jan Huntelaar told kicker: "I was not aware of that until now. Besides, it is much better to only focus on us. I think our group [which also includes Arsenal and Montpellier] is pretty open. We could come out on top or, if we fail to perform, end up third or fourth.
"That first match against Olympiakos will be special. The atmosphere will be stunning, Kyriakos Papadopoulos has already told us all about it."
Schalke, semi-finalists in the 2011 competition, are likely to give Champions League debuts to Julian Draxler and Lewis Holtby.
"I am so much looking forward to it. I have worked towards this day for a long time," Holtby, the half-English captain of Germany's Under-21s, told Der Westen. "If we get the chance, we want to win the group."
Schalke captain Bendedikt Howedes added: "It's going to be a cauldron. But Champions League matches are fun, and we worked hard to get there last season. We are massively looking forward to listening to the UCL anthem before the match."