Real Madrid and Borussia Dortmund continued their dominance of their group with victories over Ajax and Manchester City respectively as Arsenal suffered yet another defeat in Greece to Olympiakos in the Champions League.
A double from Jose Callejon and one apiece from Cristiano Ronaldo and Kaka ensured a 4-1 win for Real over Ajax, as Julian Schieber scored the only goal in Dortmund against Manchester City.
That meant Ajax go through to the Europa League, with City crashing out of Europe before the new year.
In Greece, Tomas Rosicky opened the scoring for Arsenal, before Ioannis Maniatis and Konstantinos Mitrgolou netted for Olympiakos to give the Greek side all three points.
Arsenal began a lot better than they have in recent games, looking like they might have a goal or two in them. Although, Olympiakos had the majority of the possession, and were the team that looked like would break the deadlock.
Arsene Wenger had left the majority of his first team members behind, meaning the likes of Francis Coquelin, Sebastien Squillaci and Marouane Chamakh got rare starts, with Jernade Meade also making his first Champions League appearance.
Djamel Abdoun was the standout player in the first half -- the Olympiakos playmaker showing a couple of tricks, while looking threatening going forward.
However, it was Arsenal who should have really taken the lead, when a cross into the far post was headed back into the danger area by Marouane Chamakh, who otherwise was extremely poor, making too many poor touches and decisions, with Drissa Diakite's tame clearance falling perfectly for Aaron Ramsey. The Welsh midfielder, however, badly mistimed his left-footed strike with the goal at his mercy from ten yards out.
Olympiakos then forced a couple of smart saves from Wojciech Szczesny, with Abdoun in the center of everything that was good about Olympiakos going forward.
Tomas Rosicky, making his first start this season, was looking bright and looked like the best player in an Arsenal shirt. The Czech midfielder was duly rewarded, scoring Arsenal's only goal.
Gervinho made a driving run down the right, before cutting the ball back smartly to Rosicky who fired in a first time shot past Roy Carroll in the 38th minute.
The second half saw Arsenal start the better side, controlling possession, even if not quite creating any real chances, with Andrey Arshavin, who came on at halftime for Rosicky, firing a header wide.
Olympiakos slowly got back into the game, and after a couple of half chances went astray, forced a save from Szczesny. Paulo Machado got a free header from a cross down the right, with the Arsenal goalkeeper making a full-length dive to hook the ball for a corner.
Off the ensuing setpiece, Olympiakos equalized. The cross came in, after a couple of rebounds, took a deflection of Ramsey, and fell perfectly for Ioannis Maniatis to slot the ball home in the 65th minute.
Rafik Djebbour then had a splendid chance to give Olympiakos the lead, but skewed his header, from six yards out, just wide. Leonardo Jardim brought on his prime striker Konstantinos Mitrgolou for Abdoun, and he made an impact within a minute of coming on. The forward, who also scored at the Emirates in the reverse fixture, got the ball just outside the Arsenal penalty area, before cutting onto his right foot and curling a perfect strike into the bottom corner past Szczesny's left.
Arsenal did not even remotely threaten after going down, as the Gunners lost to the Greek side for the third straight time away in the Champions League.
The other Group B game between Montpellier and Schalke ended 1-1, meaning a win for Arsenal would have made them group winners. However, Schalke now top the group and face the prospect of easier opposition, while Arsenal, as has been the norm, could face the likes of Barcelona in the last-16.
Results: Group A: Dinamo Zagreb 1-1 Dynamo Kyiv; PSG 2-1 Porto. Group B: Olympiakos 2-1 Arsenal; Montpellier 1-1 Schalke. Group C: AC Milan 0-1 Zenit; Malaga 2-2 Anderlecht. Group D: Real Madrid 4-1 Ajax; Borussia Dortmund 1-0 Manchester City.