Schalke and Arsenal will be vying for top spot in Group B when matchday six gets underway on Tuesday.
Both clubs have already qualified for the knockout phase with a game to spare in the UEFA Champions League but there is still plenty to play for.
Topping the group would mean avoiding a potential round-of-16 clash against the likes of Barcelona, Manchester United and Borussia Dortmund.
Schalke travels to France on Tuesday to battle with French champions Montpellier, who are set to bow out of the competition without a whimper.
Montpellier shocked the football world when they lifted the Ligue 1 title last season but have looked out of their depth in the Champions League this year, claiming just one point from their trip to Schalke.
Huub Stevens’ Schalke are guaranteed to win the group if they emerge victorious at the Stade de la Mosson but failure to win could hand Arsenal top spot if the English outfit beat Olympiakos.
Schalke have gone off the boil in the Bundesliga recently, failing to win their past four games but their Champions League form paints a different picture.
The German club have lost just once in their past eight European away trips – their only defeat in that period coming against Premier League powerhouse Manchester United last season.
And Dutch international striker Klaas-Jan Huntelaar has led the way with four goals this competition.
Arsenal, on the other hand, jets out to Greece on Tuesday knowing victory against Olympiakos may not be enough to leapfrog Schalke.
The 2005/06 runners-up, who have already qualified from the group stage for the 13th successive year, need to win in Greece and hope Schalke slip up at Montpellier with either a draw or loss.
However, based on Arsenal’s current form, victory against Olympiakos is no sure thing.
Arsenal Wenger’s men have only won one of its past six Premier League fixtures, a run that has seen them slip down to 10th in the standings, 15 points behind pacesetters United.
And Arsenal’s most recent trip to the Georgios Karaiskakis Stadium resulted in a 3-1 defeat.