Arsenal endured a nervous night as they lost 1-0 to Greek side Olympiakos on Thursday but still progressed into the Europa League quarter-finals 3-2 on aggregate.
After a 3-1 victory in Athens last week and reaching halftime unscathed in the return, Arsenal looked comfortable.
But when Youssef El Arabi's deflected shot left Bernd Leno wrong-footed early in the second half it gave the visitors hope and increased the tension among the home ranks.
Arsenal wasted several late chances to ease the jitters with captain Pierre-Emerick Aubameyang, restored to the starting line-up being left out of Sunday's north London derby for disciplinary reasons, guilty of a poor miss.
Olympiakos had Ousseynou Ba sent off late on and Arsenal were spared any late dramas as they avenged last season's elimination by the Greek champions to take their place in Friday's last-eight draw.
"After we conceded, we got better and got more control but we put ourselves in a difficult position," Arsenal manager Mikel Arteta said. "We gave them some belief, which you cannot give to the opponent. We'll get better."
Olympiakos will take pride from a third successive away win against Arsenal but the damage was done in the first leg when they conceded two late goals having equalised.
Arsenal were comfortable until a loose ball by Dani Ceballos led to El-Arabi's goal which gave the visitors hope.
As Olympiakos pushed forward they allowed gaps at the back and Arsenal should have capitalised with substitute Martin Odegaard firing over and Nicolas Pepe having a goalbound effort deflected away while Aubameyang could have had a hat-trick.
"It's true that we missed a lot of chances, I think we created enough chances to win the game, but still -- we were nowhere near the level we should be at," Arteta said.
Arsenal have now made it to the quarter-finals for the fourth time in their last five Europa League/UEFA Cup campaigns.
(Reporting by Martyn Herman, editing by Ed Osmond)
