The Spanish champions beat city rivals Real Madrid in La Liga at the weekend and will look to go one better than last season in Europe. Last season's runners-up Atletico Madrid will begin their Champions League campaign on a high after defeating Real Madrid on Saturday.
Diego Simeone's men were the surprise package of the 2013-14 competition, reaching the final in which they were beaten 4-1 after extra time by neighbours Real.
But the scoreline did not tell the full story of a game that Atletico led 1-0 until the 93rd minute, when Sergio Ramos' scored a last-ditch equaliser.
Real took control thereafter with Simeone's side ultimately denied a remarkable double having won La Liga for the first time since 1996.
A close-season exodus followed when the likes of Diego Costa and Thibaut Courtois left the club, although Atletico responded by doing some shrewd business of their own.
And Simeone's side have not skipped a beat, following up a two-legged Supercopa de Espana win over Real by picking up seven points from their first three La Liga games.
So impressive have their efforts been that some have suggested that this team is stronger than the one that finished last term.
"I had to say if this team is better or worse because we have different players," said talismanic centre-back Diego Godin.
"Things change but the important thing is that the team continues with the same mentality. That's the key."
The most impressive of those performances came on Saturday, when Arda Turan's goal secured a 2-1 La Liga triumph at the Santiago Bernabeu.
It is, therefore, with huge confidence that Atletico head to Greece to face an Olympiacos side on Tuesday who have also begun this season with two wins and a draw domestically.
The Spanish side will certainly glean plenty of confidence from last term, when they went unbeaten in all six away games - including eye-catching wins against Porto, Milan and Chelsea.
But Olympikcos are dominant at home, epitomised by them winning 16 of their 17 league fixtures at the Karaiskakis Stadium in 2013-14.
Atletico have concerns over the fitness of Cristian Rodriguez, who missed the Real game through a calf injury sustained when on international duty with Uruguay.
The Greek champions are likely to be without Giannis Maniatis, who has been sidelined since August 30 with a left ankle sprain, although Dimitris Siovas is edging towards a comeback from a long-term injury.
Group A rivals Olympiakos and Atletico last met in the European Cup Winners' Cup quarter-finals in 1992-93, when the Spaniards prevailed 4-2 on aggregate.
The Argentine highlighted the strength of their Greek opponents in front of their home support and is anticipating a difficult night's work on Tuesday.
Diego Simeone says Atletico Madrid will face their most difficult test in Champions League Group A when they take on Olympiakos in Greece on Tuesday.
The Greek Super League champions won 16 of their 17 league fixtures at home last season, as well as defeating Manchester United in the first leg of their last-16 European tie before exiting the competition after a second leg defeat.
Atleti finished runners-up themselves in the competition last term, but Simeone pointed out just how tough a proposition Olympiakos could prove to be.
He said: "Tomorrow morning we will decide the starting lineup. This will probably be the most difficult game in the group; Olympiakos have a very strong home record and passionate fans. We had a great season last year. But that's in the past. We are starting from scratch again. We are building the team day by day."
The Argentine is familiar with Olympiakos boss Michel having come up against him during his playing days and was quick to praise him for giving his side an identifiable style of play.
"I''ve played against Míchel as a player and coach," he added.
"Míchel had a great run with Olympiakos in the Champions league. He's succeeded in giving Olympiakos a distinct style and character. He has put his stamp on the team."
