With a tie against either Mura or Ludogorets up for grabs in the next round, both sides will fancy their chances of taking one step closer to the group stages.
Though Olympiacos started off their European campaign on the right foot last week - beating Azeri champions Neftchi 1-0 by virtue of midfielder Mady Camara's 29th-minute goal - such a slim margin of victory means that Wednesday's return leg at the Bakcell Arena is far from a foregone conclusion.
Having strolled to the Greek Super League title last term, the Athens club entered the qualifying process at the second round stage, where they were expected to overcome a team that has never before made it to the promised land of the Champions League proper. However, Camara's sending off - just minutes after his breakthrough goal - saw them cede the initiative, before Neftchi were also reduced to ten men after the break.
Overseen by Portuguese coach Pedro Martins, Olympiacos finished a remarkable 26 points clear of closest challengers PAOK last term and have been a regular fixture in the group phase during recent years, but rarely progress further.
Since their return from the summer break, the Erythrolefki warmed up with a series of friendlies - beating Krasnodar and CSKA Sofia, but losing to Austrian outfits RB Salzburg and Wolfsberger - before a match with Galatasaray was called off amid acrimonious circumstances.
Martins could feasibly claim, therefore, that his team were a little undercooked before meeting Neftchi at the Karaiskakis Stadium, but if they are to be involved in the glamour ties during the autumn, they must improve or face the prospect of dropping into the Europa League.
After they dared to dream before slipping out in the last 16 of the continent's second-tier competition to Arsenal last season, there can be no excuses for failing to overcome an opponent with minimal European pedigree this week.
Though Neftchi were the first Azeri team to make the group stage of any UEFA competition back in 2012 - finishing bottom, but achieving memorable draws with Partizan Belgrade and Italian giants Inter Milan - the Baku-based outfit have rarely come close to a return in the intervening years.
Yet to start the defence of their first league title since 2013, earlier this month, the Neftciler came through their first round qualifying tie with Dinamo Tbilisi with a 4-2 aggregate victory; winning 2-1 both home and away.
They had previously posted a pre-season friendly win over Spartak Moscow too, with their record stretching back to the climax of last season showing eight wins from their last 12 games in all.
Such a run demonstrates the relatively strong squad available to head coach Samir Abbasov, so - particularly given their competitive first leg performance, when they had numerous shots on target - they could feasibly upset the odds by toppling a Greek giant in Baku.
Due to his indiscipline in the first leg, Olympiacos will be without Guinean midfielder Mady Camara, so compatriot and namesake Aguibou Camara could be in line for a first start since signing from Lille, or teenager Vasilis Sourlis may be given the nod after featuring as a substitute last week.
Head coach Pedro Martins signed Czech Republic goalkeeper Tomas Vaclik earlier this month, to replace Premier League-bound Jose Sa (who has joined Wolverhampton Wanderers), but young stopper Konstantinos Tzolakis is expected to keep his place for now.
Neftchi, meanwhile, have some selection issues of their own, as Mirabdulla Abbasov was brought on to replace star striker Namiq Alasgarov at the break last Wednesday, due to an injury for the former Qarabag man. Therefore, doubts linger over his availability this week, while Mert Celik's first-leg dismissal means that the hosts' three-man defence must be changed - Omar Buludov is favourite to deputise.
Paraguayan forward Cesar Meza Colli will shoulder the goalscoring burden in the Neftchi front two, particularly if Alasgarov cannot recover in time.
Neftchi Baku possible starting lineup:
Mammadov; Stankovic, Mbodj, Buludov; Harramiz, Kane, Mahmudov, Bougrine, Lawal; Colli, Abbasov
Olympiacos possible starting lineup:
Tzolakis; Lala, Semedo, Markovic, Reabciuk; Bouchalakis, Malong; Masouras, Valbuena, Randelovic; Hassan
We say: Neftchi Baku 1-1 Olympiacos
Having shown their mettle during the opening 90 minutes of this tie, the home side have certainly not squandered their hard-earned momentum, and can catch Olympiacos out at least once.
Neftchi, though, are lacking tried and tested performers at this level, so one of the visitors' many forward options can salvage a draw and - by the narrowest of margins - help them progress on aggregate.
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