Bayern Munich players Jerome Boateng and Thiago Alcantara believe Barcelona are the favourites for this season's Champions League.
Under coach Pep Guardiola, Bayern have twice reached the semifinals of the Champions League, but have been unable to get past Spanish opponents at that stage.
In 2014, they were eliminated by Real Madrid and, last season, Barcelona ended the Bavarians' hopes of returning to the final they last reached in 2013.
Guardiola has entered the final 12 months of his current deal at Bayern, and he is under pressure to bring the Champions League title back to Munich.
Speaking to reporters ahead of Wednesday's match at Olympiakos, Boateng said: "I wouldn't say that the chances [of winning the Champions League] are bigger this season. Barcelona are the top favourites."
Thiago, who signed for Bayern from the Camp Nou in 2013, added: "Barcelona are the team to beat."
However, the Spain international, who recently prolonged his contract at Bayern until 2019, said that caution should not be mistaken for fear.
"I am never scared of any opponent," Thiago said.
Bayern Munich, who recorded a late 2-1 victory against FC Augsburg at the weekend, start their Champions League campaign away to Olympiakos and Boateng expects a rampant crowd to give them the opposite of a warm reception.
"They hit the gas for 90 minutes! The fans never stop singing and get right behind their team," Boateng said. "It'll be a very hostile atmosphere."
"It's a big game for Olympiakos. They'll be very aggressive and dig deep. We have to concentrate hard, resist them and show from the start that we intend to win."