Chances were few and far between in a match that had been billed as boasting two of Europe’s more attacking sides. For Napoli in-form forwards Edinson Cavani and Ezequiel Lavezzi struggled to get into the game, with the former having one effort disallowed for offside and both denied by good stops from Diego Lopez.
Villarreal were no better, struggling to get the ball to Nilmar and Giuseppe Rossi and only going close when Borja Valero fired wide from the left.
Napoli defender Salvatore Aronica was shown a red card in injury time, booked twice but shaking English referee Mark Clattenburg’s hand after a cynical foul on Nilmar.
The second leg takes place next Thursday.