The Danish side survived a late onslaught after Ján Greguš's red card midway through the second half as Andreas Cornelius's header earned them a share of the Group G spoils.
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København, down to ten men for the last 25 minutes, resisted concerted late pressure to earn a 1-1 draw at Porto in their Group G opener.
The Danish visitors had picked up at least a point on their three previous UEFA Champions League group stage starts, but Otávio's early goal – stemming from an FCK mistake and a sublime André Silva touch – threatened that record.
However, atoning for a first-half miss, Andreas Cornelius showed determination to send a looping header over Iker Casillas to level, and FCK held out for the draw despite Ján Greguš's second-half dismissal and a frenetic finale.
Key player: Otávio
When Porto were at their best in the first period, Otávio was the player through whom most of the hosts' attacking play moved. Linking wonderfully with striker André Silva before smashing in the opening goal, the 21-year-old Brazilian epitomised the attacking verve Porto aspire to play with on a regular basis.
Early lesson for FCK
Though they got a point, Porto's goal was a lesson for the visitors in just how much of a step up this competition is. Mathias Jørgensen's cushioned header to Thomas Delaney on the edge of his own box might have worked elsewhere, but not at this level. Otávio's anticipation as he robbed Delaney before scoring was too much for FCK. They need to learn. Quickly.
Porto still improving
Having endured four years without a trophy, Porto have charged coach Nuno Espírito Santo with returning the Dragões to former glory. The 42-year-old's side still appear a team in transition. Porto's strong first-half showing contrasted sharply with their lethargic post-interval efforts. Even with København reduced to ten, a change in formation and the introduction of Laurent Depoitre failed to inspire the hosts.
Paul Bryan, Porto (@UEFAcomPaulB)
A stirring second half from København's ten men served to frustrate Porto, whose own failings following a promising start suggested they must improve if they are to make strides in the UEFA Champions League this season.
Ian Holyman, København (@UEFAcomIanH)
There is little doubt the visitors will head home absolutely smitten with their point. More than the result, though, Ståle Solbakken and his squad will be heartened by their ability to match Porto, the most Europe-savvy of their group stage opponents. Before kick-off, captain Delaney had hinted his side could hope for no more than third place ... he might now be revising that opinion.