Almost an hour into a tie that burned imperceptibly until its unlikely late combustion, Arsenal were treated to a glimpse of exactly who was in charge. They had won possession just outside Porto’s penalty area and Kai Havertz, advancing with purpose, saw a chance to play Gabriel Martinelli through. Instead the ball ended up with Pepe, gimlet-eyed and perfectly positioned. Seconds later he had carried it 30 yards up the pitch before sliding a precise pass through the midfield to Evanilson, sending the hosts away once again. There was a sense he could have done it all again with a blindfold. On Monday, Pepe will turn 41. Blowing out all those candles may take more exertion than a pallid Arsenal attack demanded but that moment of authority, the brushing aside of nascent threat, the upright strut that has been a feature of elite football for two decades, spoke of the bigger picture. Arsenal’s past failures in the last 16 have been intricately documented but there had justifiably been high anticipation around their return. In the event they failed to land a blow on Pepe and Porto: old dogs who had little attention of standing around to watch new tricks. Long after Arsenal had made haste down the tunnel, Porto’s players huddled in a circle while Estádio Do Dragão’s choirs went through the repertoire of club anthems. The song for Mikel Arteta was rather more familiar: perhaps a footballing equivalent of the melancholic fado ballads that echo around some of the local bars. It is a tune that laments naivety and foggy decision making against continental opponents schooled in the art of setting traps. Arteta heard it often enough as a player in north London and, after Martinelli sought Bukayo Saka with a needless Hollywood pass in the final minute of added time, it struck up again. The Porto goalkeeper, Diogo Costa, had spoken cryptically of exposing Arsenal’s weaknesses and Galeno honoured the promise by arcing a thrilling finish around David Raya. Costa’s optimism apart, the noise around Porto had been profoundly negative in the buildup. They are currently passengers in the Portuguese title race and the long-serving Sérgio Conceição, a rival to Arteta in the touchline expressiveness stakes, has felt the wrath of their support. Lore had it that they were not up to the level of knockout Champions League football this time. As proceedings unfolded, that became irrelevant. Porto have passed the group stage seven times in the last decade: if nothing else, they knew the level intimately. That knowledge helped Conceição, no longer one of Europe’s bright young coaches at 49 but still a formidable operator, win the battle of strategies against his counterpart. Porto were compact, athletic, quick to close space and happy to test Arsenal on the counter. While Pepe, who made up for the lack of a centre-forward to needle by contributing to penalty box chaos at the visitors’ set pieces, purred at the back there were impressive exhibitions of ball carrying from his 26-year-old namesake further upfield. Conceição knew Porto would have to pick their moments but they retained a threat all evening. By contrast Arsenal carried little menace. It was one of those nights when Gabriel Jesus, still sidelined, might have infused his peers with an added shot of intensity. They had not failed to land a shot on target since losing at Nottingham Forest in the FA Cup third round a little over two years ago. That particular match infuriated Arteta, who fumed about a lack of hunger afterwards. Such an accusation would not have been valid this time; instead Arteta detected a purposelessness, perhaps a timidity in the face of Porto’s physicality, and above all a lack of clarity that ultimately brought their undoing. There will be no rush to proclaim this a terminal setback. Arsenal have the tools to pull well clear at the Emirates in just under three weeks; they will still be favoured to reach a first quarter-final in 14 years and will pose considerably more threat than the headers from their centre-backs, William Saliba and Gabriel Magalhães, that passed for their best chances here. If the history books are to be leant upon in foreboding, they can also be wielded for the opposite effect: they made it to that stage in 2010 by beating Porto 5-0 at home, having lost by a one-goal margin in the first leg. But, like his team, Arteta must prove he has learned from bad experiences. During his reign Arsenal have come unstuck in second legs at home against Olympiakos and, surprisingly last season, Sporting. He cannot afford it to become a recurring pattern. Perhaps, a decade or so down the line, some of Arteta’s players will have matched Pepe’s three Champions League titles with Real Madrid. Maybe they will be dealing lessons to highly favoured upstarts and reminding them that, for all the change in modern football and all the Premier League’s outward supremacy, history and stature still act as levellers when it matters. This may only have been the slightest of pebbles on the road, but Arsenal’s coronation as contenders must wait a little longer.