Arsenal progressed after winning the tie 3-2 on aggregate, but for Mikel Arteta, it was a more nervous evening than planned, and overall a lacklustre performance from his side.
Mikel Arteta's side had been in control without really hitting top gear in the first half. Pierre-Emerick Aubameyang and Nicolas Pepe both had chances to score, but the Gunners looked lethargic, and perhaps complacent. Olympiacos sensed the opportunity to strike back in the tie, and Youssef El-Arabi, who scored in the first leg, found the scoresheet again when he put the visitors ahead on the night with help from a Gabriel deflection.
Ultimately, though, despite finishing the game on the front foot, Olympiakos fell two goals short over the tie, and it's Arsenal who go into tomorrow's quarterfinal draw for the third time in four seasons.
Arsenal weren't at their best but still created five or six clear-cut chances. On another evening, Aubameyang could have had a hat trick.
Arsenal once again pressed the self-destruct button. They were dominating possession and weren't troubled but went a goal behind after a slow start to the second half. Moreover, it's now 11 games in a row without a clean sheet.
Manager rating out of 10
5 -- The Spaniard didn't quite get the right mix or shape. The right-hand side looked weak in particular, while the central axis of Granit Xhaka and Dani Ceballos was poor. His changes did improve things, but overall the team looked tired. He got away with it, but better opponents lay in wait.
Player ratings (1-10; 10 = best. Players introduced after 70 minutes get no rating)
GK Bernd Leno, 5 -- The German stopper made a vital save in the first half to deny El-Arabi, who broke free from a simple pass through the middle. Unfortunately, Leno could do little to deny the striker when through again, when the striker's shot went in via a big deflection.
DF Hector Bellerin, 4 -- The Bellerin-Pepe combination on the right didn't work, and Bellerin was guilty of losing possession on multiple occasions. It was a surprise he lasted so long before being substituted.
DF David Luiz, 6 -- Luiz made some decent interceptions but generally looked tired. He was certainly guilty of letting El-Arabi come inside too easily as Olympiakos took the lead.
DF Gabriel, 6 -- Gabriel had a solid evening. He made more clearances and won more aerial battles than his teammates, but he was unlucky to see El-Arabi's shot deflect off him and into the net.
DF Kieran Tierney, 6 -- Tierney didn't have his best evening, but he still showed quality on the left that highlighted the lack of quality on the right. That said, he looked leggy all evening.
MF Dani Ceballos, 6 -- The Spaniard played in the No.10 role and contributed two excellent passes, first to Pepe and then Aubameyang. Sadly, neither player could make the most of the opportunities.
MF Mohamed Elneny, 5 -- Elneny was replaced for giving away the ball too often after a series of turnovers in the Arsenal half.
MF Granit Xhaka, 5 -- Arsenal looked a different team to the one that beat Spurs at the weekend, and there was too much sideways and backward passing with Xhaka one of the main culprits.
FW Nicolas Pepe, 7 -- In for the injured Bukayo Saka, he had an excellent opportunity to break the deadlock in the first half. He received an excellent pass from Ceballos and rounded the keeper, but he could only find the side netting. He had another effort after the break when put through by Emile Smith-Rowe, but his shot lacked any power or pace.
FW Pierre-Emerick Aubameyang, 5 -- The striker returned after missing the London derby and had a very tentative opening 45 minutes. His best chance followed a neat through ball from Ceballos, but he could only blaze over the bar. In the second half, he had a one-on-one but lacked conviction, and his dinked effort lacked composure. One last late effort was well saved.
FW Emile-Smith Rowe, 5 -- Sat on the left of a front three and had the first shot of the game. Unfortunately, it was blocked by Sokratis and rebounded straight back into Smith-Rowe's face. Looked tired throughout.
MF Thomas Partey, 5 -- Partey brought time and composure on the ball, but even he was guilty of losing the ball in his own half and around the box.
MF Martin Odegaard, 7 -- The Norwegian brought some quality to the Arsenal midfield that had been lacking. His main issue was that he dropped deep to get the ball when he probably needed to stay further forward.
FW Gabriel Martinelli, N/R -- It was a welcome appearance for the young forward, and his pace caused Olympiakos problems. He contributed a nice run and passed to Aubemayang who couldn't quite find the net.
DF Calum Chambers, N/R -- Brought on to protect the aggregate scoreline, he steadied the ship on the right-hand side.