Olympiacos 0 Arsenal 3
Olivier Giroud inspired Arsenal to complete a Champions League group stage comeback as his hat-trick at Olympiacos sealed their place in the last 16.
Going into the game having lost three of their previous five fixtures, the Gunners needed to win by two goals or more at the Karaiskakis Stadium or better the 3-2 defeat they suffered at home to the Greek champions in September.
With seven key first-team players missing through injury, Arsene Wenger recalled Theo Walcott after his recovery from a calf problem - but it was Giroud who would produce the goods when it mattered as Arsenal made light work of a seemingly difficult task to seal a 3-0 win.
For Giroud it would have been all the more sweet given he had been sent off in the 2-1 defeat at Dinamo Zagreb which started a run of poor results that led to tonight's scenario.
Arsenal become just the eighth side to advance through their group having taken three points or fewer from their opening four matches and Wenger will now be hoping to avoid the big names as they will come up against a group winner in the next round.
The Gunners took their time as they felt their way into the contest but finally stirred as Joel Campbell's cutback was struck goalwards by Mathieu Flamini, with a deflection off Manuel da Costa taking the ball onto the crossbar.
But the opener came just moments later as Mesut Ozil produced a sublime pass to set Aaron Ramsey away.
His near-post cross was met by the head of Giroud and the ball squeezed over the line as Olympiacos goalkeeper Roberto was unable to deal with it.
It was the hosts who nearly got the game's next goal as another sloppy pass from Hector Bellerin left Arsenal exposed and Brown Ideye's cross was turned inches over his own crossbar by Laurent Koscielny as the game remained finely poised at the interval.
There was concern for Giroud at the start of the second half as he fell awkwardly on his ankle while helping out his defence.
But he soon got himself back on the pitch and soon doubled Arsenal's lead after another well-worked move.
Ozil again started everything with a clipped pass to Campbell, with the former Olympiacos loanee controlling well under pressure before sliding a perfect pass into the path of Giroud for the France striker to sweep home.
Walcott came close to adding a third to give Wenger's men some breathing space but his effort was blocked behind for a corner.
Petr Cech then showed just why Wenger was so keen to sign him in the summer as he pushed away a curling Kostas Fortounis shot with the hosts looking for the one goal they needed to advance at Arsenal's expense.
Ideye should have done better when picked out in front of goal but Per Mertesacker was on hand to clear before the former West Brom forward could pounce.
Olympiacos had begun to set siege to Cech's goal but they were undone when referee Nicola Rizzoli pointed to the penalty spot as Nacho Monreal's shot was blocked by the arm of the diving Omar Elabdellaoui.
Giroud duly despatched the resulting penalty to complete his hat-trick and send Arsenal into Monday's draw for the first knock-out stage as they saw out the remainder of the contest with minimal fuss.
Hat-trick hero Giroud said on BT Sport: "It's fantastic for me and the team. We are really pleased to go through tonight. We were not in a good position and finally we've done it so we're very pleased for the club and the fans.
"We want to go as far as we can. Our target is maybe to reach the quarter-finals. Personally it is my fourth year here and I've never played a quarter-finals so we will see the draw, have a rest, and open a new page in the Champions League in February."
Arsene Wenger hailed a "perfect game" from his team.
"I told you before the game it would be a great escape, and I must say I'm very proud of the team," he said. "We needed to be right on the mental side and right on the tactical side as well. We knew we had to push for the third goal because it's very dangerous at 2-0, and we had the perfect game.
"Nine times out of 10 in that position you are out of the group. We needed something special to switch it on and come back like we did tonight. We needed a complete team performance and that's what it was.
"Maybe it is a lucky year for us in the Champions League. You never know."
