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The reigning Serie A champion looked to be on course for three precious points when Scott McTominay rose to meet a left-sided corner from Eljif Elmas and plant a firm header into the top-right corner.

That goal came seven minutes before half-time and shortly after Copenhagen were reduced to 10 men, with captain Thomas Delaney seeing red for a high lunge on Stanislav Lobotka, with his punishment upgraded after a VAR review.

But Napoli failed to capitalise on its numerical advantage after the interval, and Copenhagen were gifted a golden chance to equalise when Alessandro Buongiorno chopped Mohamed Elyounoussi down in the area after 69 minutes.

Jordan Larsson's tame spot-kick was saved by Vanja Milinkovic-Savic, but the Copenhagen forward pounced on the rebound to tap home.

Substitute Lorenzo Lucca missed a glorious chance to win it for Napoli late on, and they remain 23rd in the standings – level on points with Copenhagen in 24th – with a showdown with Chelsea to come next week.

Ajax induced further anxiety among Napoli's supporters by beating Villarreal 2-1, with Oliver Edvardsen scoring an 89th-minute winner.

The Eredivisie giant could still reach the play-offs despite losing its first five games in this season's competition, with Olympiacos set to visit Amsterdam in its final fixture.