Two enterprising, attacking sides crafted a beautiful game at the Bernabeu, featuring fast, skilful play, plenty of edge, and some lovely goals.
Madrid almost went in front after 23 seconds, Pepe Reina beating away Karim Benzema's effort after he was teed-up by Cristiano Ronaldo. But even though they did not have much of the ball, Napoli looked dangerous on the break, taking the lead on eight minutes when Marek Hamsik fed Lorenzo Insigne, whose instant shot caught Kaylor Navas out of position and resulted in a brilliant goal.
At no point, though, did Napoli look capable of holding onto their lead, and after various missed chances, Dani Carvajal crossed superbly with the outside of his right foot for Karim Benzema to head home the equaliser.
Napoli actually started the second half in the ascendancy, but Ronaldo, playing down the right, pulled back perfectly for Kroos to punch in a low finish on 49 minutes before, shortly afterwards, Casemiro murdered home a volley to complete the scoring.
Really, Madrid ought to have scored at least twice more, but Napoli will also regret Dries Mertens' miss that would have set them up perfectly for the return, and in the event, both sides looked relatively satisfied with 3-1; Madrid will reckon the tie just about over, and Napoli will reckon it just about alive.