Olympiacos have omitted striker Emmanuel Emenike from their squad list for Tuesday night's (31 October) Champions League return fixture against Barcelona in Piraeus, while Seba and El Fardou Mohamed Ben Nabouhane both remain sidelined.
Former Nigeria international Emenike missed the initial 3-1 loss at the Nou Camp a fortnight ago with a calf injury suffered during the defeat to Atromitos on 1 October but made his return to action last week by coming off the bench to score the third and final goal in a comfortable Greek Cup victory over second-tier Acharnaikos.
The ex-West Ham United frontman started the hugely disappointing loss to arch-rivals Panathinaikos on Saturday, although was notable by his absence from Takis Lemonis' preliminary 20-man squad to face Barcelona.
Fellow striker Ben Nabouhane has not played since limping off after just 13 minutes of that meeting with league leaders Atromitos due to a hip strain, meaning that once again Olympiacos have opted for just the one forward in Serbian Uros Djurdjevic.
Brazilian winger Seba, meanwhile, recently underwent arthroscopy surgery on his knee and is not expected to feature again until after the forthcoming international break.
Midfielder Sasa Zdjelar has also been left out by Lemonis along with fourth-string teenage goalkeeper Dimitris Skafidas. Pape Abou Cisse, Hrvoje Milic, Andre Martins and Karim Ansarifard are not currently eligible for European competition.
Barcelona will be without Gerard Pique following the Catalan's red card on matchday three, while Andres Iniesta, Ousmane Dembele, Rafinha, Aleix Vidal and Arda Turan are also out.
Javier Mascherano and Thomas Vermaelen have travelled to Greece after missing the 2-0 win over Athletic Club Bilbao with a foot infection and hip problems respectively, although manager Ernesto Valverde is hopeful that both could be available to play.
If they are not, and with only goalkeeper Adrian Ortola and midfielder Carles Alena promoted from the B team, then Samuel Umtiti would stand alone as Barcelona's only fit senior centre-back.
"Since the game against Murcia he's [Mascherano] had a foot infection. We need to have a look at that," Valverde, who won three Greek SuperLeague titles and two Greek Cups over two separate spells in charge of Olympiacos, told reporters in his pre-match press conference on Monday evening.
"We are looking at him in training today. We'll find out how he is, Vermaelen has also had some issues but he's fit. Hopefully they can both play tomorrow."
Five-time European champions Barcelona have won all three of their group games to date in 2017-18 while only conceding one goal and will seal a spot in the last 16 if they win on Tuesday and Sporting CP fail to beat Juventus in Lisbon.
Olympiacos, meanwhile, have yet to muster a single point and will be unable to progress if they lose to the Blaugrana and Juventus avoid defeat.