Two stunning late free-kicks from Nicolas Pepe saw Arsenal come from behind to beat Vitoria 3-2 after former Tottenham wonderkid Marcus Edwards had terrorised the Gunners at the Emirates.
Edwards opened the scoring with a fine turn and finish inside the penalty area on eight minutes but the home side equalised through teenager Gabriel Martinelli on 32 minutes.
Vitoria deservedly restored their lead just six minutes later and looked to have done enough to take all three points before Pepe bent home a free-kick on 80 minutes and added a second in injury time to stun Vitoria.
Vitoria – with a lengthy injury-list and resting some players ahead of Sunday’s Primeira Liga clash at Sporting – will ultimately leave London disappointed that they failed to secure a point, let alone the three they looked destined for.
Andre Almeida had a good early chance to put the visitors ahead as he turned Rob Holding with ease before a tame strike at Emiliano Martinez.
But Arsenal did not heed the warning and fell behind soon after as Almeida got the better of Kieran Tierney before squaring for ex-Spurs man Edwards to coolly control and slot home.
Alexandre Lacazette, starting for the first time since undergoing ankle surgery, scuffed a shot wide as the Gunners looked for an immediate response – but it was Vitoria who were still enjoying the majority of the possession.
Emile Smith Rowe’s jink and shot was deflected behind but it was Davidson who skied a fine chance to double Vitoria’s lead as he was picked out from a routine free-kick.
Martinelli, who scored twice in the win over Standard Liege in Arsenal’s last outing in this competition, failed to connect with a Hector Bellerin cross at the near-post as the home side finally came to life at the half-hour mark.
But he would make amends moments later as, with Vitoria goalkeeper Miguel Silva wandering off his line, he headed home Tierney’s cross to equalise.
Forall their battling to get back into the game, Arsenal soon allowed their Portuguese visitors to regain the lead as Ainsley Maitland-Niles was robbed of possession by Davidson, who broke forward and hit the post before Duarte thrashed home the rebound.
More than a smattering of jeers greeted the half-time whistle and Emery responded to the first-half performance by introducing both Matteo Guendouzi and Dani Ceballos at the break.
Shkodran Mustafi headed wide early in the second-half before Martinez had to be at his best to keep out Denis-Will Poha’s close-range effort. Smith Rowe was then guilty of skewing a shot wide when well-placed as Arsenal, much like in Monday’s defeat, toiled to create chances to salvage a result.
That saw the flow of the game change as Martinelli was denied by Silva, who then did well to hold onto Holding’s downward header – but there was nothing he could do to prevent Pepe stealing the headlines with an injury-time free-kick – with Emery the only man involved with Arsenal not hitting the roof at the winning strike.