To finish at the top of Group B, Arsenal must win in Greece and rely on last-place Montpellier to take points off Schalke in France.
London: Already assured of spots in the last 16 of the Champions League, Schalke and Arsenal still have first place to play for on Tuesday when they complete their group-stage campaigns. Arsenal travels to Olympiakos knowing the perils of finishing second - the last time it happened, in 2010, the English team was drawn against Barcelona in the knockout stage and was beaten over two legs by the eventual champions.
To finish at the top of Group B, Arsenal must win in Greece and rely on last-place Montpellier to take points off Schalke in France. The fight for first place keeps alive any real interest in the group, with Olympiakos assured of third place and a spot in the Europa League.
Arsenal manager Arsene Wenger had pledged to take a full-strength squad to Olympiakos, although the team's recent struggles in the Premier League may persuade him to change his mind and rest some key players. The London club has slipped to 10th place in the standings following its worst start to a league campaign after 15 games under Wenger. Arsenal was humiliated by Swansea on Saturday, losing 2-0 and trudging off to jeers at fulltime.
"We know that results will bring everyone together," Arsenal midfielder Mikel Arteta said. "When they don't come, people will be criticized - the manager, players and staff. The main thing is that everyone give 100 percent now." The Champions League also comes as a welcome distraction for Schalke, whose form has dipped alarmingly in the Bundesliga with just five points earned from its last six games.
"Of course we'd like to be first in the group so that we can hope for a slightly easier opponent in the knockout stage," Schalke sporting director Horst Heldt said. "But we also need a good result to give us a push for the remaining games before the winter break."
Schalke coach Huub Stevens will be without central defender Kyriakos Papadopoulos (knee) and forward Ibrahim Afellay (torn muscle). Montpellier has been taught a lesson in its first year in the Champions League but will look to bow out on a high in front of the team's fans, who have had little to shout about this season.
Having lost four of its five Champions League games, Montpellier has also drifted down to 13th place in the French league in the defense of its title. The absence of striker Olivier Giroud, who was sold to Arsenal in the offseason, is still keenly felt. Arsenal will be without France internationals Abou Diaby and Laurent Koscielny, who both have thigh problems, while Jack Wilshere - recently back from a long-term injury - is likely to be given a breather.
"There are many players who need a rest, because they are on the verge of getting injured and some played with knocks," Wenger said. "But we hope that we get a good performance at Olympiakos because it is important for us." Olympiakos playmaker Ariel Ibagaza insisted his team is eager to beat Arsenal, despite being out of contention for the last 16.
"The motivation is always there," the attacking midfielder said. "It's good for our standing in Europe." Olympiakos maintained its unbeaten start to the Greek league over the weekend, beating Platanias 2-1 to open up a 10-point lead over PAOK Thessaloniki.