Arsenal were unable to finish top in Champions League Group B as Olympiacos came from behind to win 2-1 at the Stadio Karaiskaki.
An Arsenal side containing several fringe players went in at the break 1-0 up thanks to Tomas Rosicky's strike but deserved goals from Giannis Maniatis then substitute Kostas Mitroglou in the second half denied Arsene Wenger's side the win that would have put them top with Schalke only able to draw 1-1 at Montpellier.
Wenger left senior players Jack Wilshere, Santi Cazorla, Mikel Arteta, Theo Walcott and Lukas Podolski at home and handed a first senior start to 5'3" Jernade Meade at left-back.
Gervinho snatched a shot wide of the near post early on but the Gunners' forward play in the first half was mostly poor, with the Ivorian a willing runner but often unaware of people in good positions and Marouane Chamakh ineffectual.
The Greek side - 10 points clear at the top of the Super League - carried a far greater threat. Meade was given the runaround by Paulo Machado while the triple attacking threat of Djamel Abdoun, Leandro Greco and Rafik Djebbour lurked around the box as cross after cross was dealt with by imperious Arsenal captain Thomas Vermaelen and central defensive partner Sebastien Squillaci.
The best chance of the half - other than the goal - fell however to Aaron Ramsey on 17 minutes. Olympiacos failed to deal with a corner and the ball dropped kindly for the Wales captain in the centre of the box, but he fell over the ball.
When Vermaelen was bested by Vassilis Torossidis as he peeled away to meet a corner to the back post, Wojciech Szczesny was down quickly to block the header at the foot of the post.
The opening goal arrived on 38 minutes: Gervinho looked set to send in a low cross but checked back and played a low ball towards the edge of the box which was smashed into the far corner by the arriving Rosicky.
Andrey Arshavin, the only senior player on the visitors' bench, came on for Rosicky at the break and showed signs of form from the left side.
He could have made it 2-0 around the hour mark when volleying for the near-post top corner as the ball bounced across him following good work by Chamakh, only to be denied by an excellent save from former Manchester United keeper Roy Carroll.
Olympiacos were level three minutes later, Maniatis finishing from close range after Ramsey had chested the ball down inside the box when trying to deal with a cross.
Szczesny was furious that a corner had been awarded prior to the goal as Machado's downward header had in fact shaved the post and not been tipped around it by the Pole.
On 70 minutes Machado bent a cross to the far post where Djebbour had left Carl Jenkinson for dead, but the striker somehow directed his diving header wide.
Two minutes later Mitroglou was introduced for Abdoun. He needed only a minute to make an impact, turning away on the left corner of the box before bending a lovely strike into the far bottom corner for his fourth goal in six matches in this season's competition.
With no experience to call upon Wenger only made one more change, Martin Angha on for Meade, as the Gunners saw their chances of being among the top seeds for the knockout draw slip away.
MAN OF THE MATCH:
Mitroglou (Olympiacos) - On the pitch for barely a minute when he bent a gorgeous strike into the far corner for the winning goal.
Olympiacos: Carroll 7; Torossidis 7, Conteras 6, Manolas 6, Diakite 5; Fejsa 7, Maniatis 7, Machado 7; Greco 6, Abdoun 7, Djebbour 7. Subs: Ibagaza 6, Fuster 6, Mitroglou 8
Arsenal: Szczesny 7; Jenkinson 5, Vermaelen 7, Squillaci 6, Meade 6; Coquelin 5, Rosicky 7, Ramsey 5; Oxlade-Chamberlain 5, Chamakh 5, Gervinho 5. Subs: Angha 6, Arshavin 6