Arsenal manager Mikel Arteta has conceded that his side "lacked purpose" in their agonising 1-0 loss to Porto in the first leg of their Champions League last-16 tie.
The Gunners made the trek to the Estadio do Dragao on the back of scoring 11 goals in their last two Premier League away games against Burnley and West Ham United, but their attacking excellence eluded them in Portugal.
Arteta's troops dominated the ball throughout Wednesday's first leg, but Porto's defensive wall - marshalled by 40-year-old Pepe - stifled the Gunners' threat and prevented the visitors from having a single shot on target.
Not since March 2011 against Barcelona had Arsenal not made the goalkeeper work in a Champions League match, and it had been two years since the Gunners - who also failed to assert their usual dominance from set-pieces - last failed to have a shot on target in any competitive match.
The Gunners would seemingly take an acceptable goalless draw to the Emirates for the second leg, but with four minutes of injury time on the board, Gabriel Martinelli cheaply gave the ball away, and Porto capitalised through Galeno, who found the far corner with a sensational long-range curler.
Arsenal still have 90 minutes to turn the tie on its head at the Emirates in three weeks' time, but speaking in his post-match press conference, Arteta lamented his side's passive nature and how they "gave the game away" with poor decision-making at the end.
"Obviously we're very disappointed by the way we gave the game away at the end, and not managing that situation well enough, and you get punished in the Champions League - if you cannot win it, you don't lose it," Arteta said, as quoted by arsenal.com.
"We really dominated the game, but we lacked purpose, especially in the first half to have much more aggression, to break lines, to play forward, to generate much more threat in their backline.
"In the second half, there were much better things, and we generated a lot of situations without really creating much from it, but we'll learn from it. Now it's clear, it's half time.
"If you want to be in the quarter-finals, you have to beat your opponent, that's clear, and that will be the purpose and the plan with all our supporters together to do it."
Arsenal's flow - or lack of - was not helped by constant whistle-blowing from referee Serdar Gozubuyuk, who awarded a staggering 36 free kicks on the evening - 22 for Porto and 14 for Arsenal, who also had Declan Rice booked in the first two minutes.
The £105m midfielder managed himself well while walking a tightrope for the remainder of the match, but Arteta bemoaned the official's decision to blow for a foul "every time" one of his troops touched a Porto player.
When asked about how Porto quelled his team's hitherto rampant attack with regular stoppages, Arteta added: "That's the context of the game, we knew, we prepared [for it]. That's something the referee has to manage; we cannot do anything about it. And we're going to have to handle it and play our game.
"Credit to them, they defended well, but it's true that when we got into certain situations, we didn't finish the action or put the right final ball in the cross or from set-pieces as well. Every time we were touching somebody, it seemed to be a foul before we even kicked the ball. So, we will learn from that and be better. "
Arsenal now turn their attention back to Premier League matters on Saturday evening, when Newcastle United stop over at the Emirates seeking their first top-flight double over the Gunners since 1994-95.
