Nicolas Pepe scored twice to earn Arsenal an undeserving win against Guimaraes of Portugal in the Europa League fixture.
Arsenal stepped into the game with full confidence as they remained unbeaten in the group stage and having won all its fixtures.
The visitors turned the table around as they took control of the game from the start causing trouble in every position.
In the 9th minute Edwards made it 1-0 for the visitors beating Martinez from the far end of the net.
In the 32nd minute Brazilian youngster Martinelli leveled things up for the Gunners converting through a header when goalkeeper Joao Miguel left his post.
Guimaraes responded back with the second goal five minutes later through Duarte who comfortably sent the ball behind the net from a nicely taken shot.
Coach Unai Emery made two second half changes bringing in Guendouzi and Ceballos to strengthen the midfield and bring in creativity int the game.
French striker Lacazette was substituted with Ivory Coast forward Nicolas Pepe who drew things level in the 80th minute through a free kick.
He was at it again at the extra time when Guendouzi was brought down inches away from the penalty box.
He calmly took the free kick to retain the Gunners at the top of the table and record a win after a poor performance against Sheffield on Monday.