Naples (Italy): Liverpool manager Jurgen Klopp said it was "clear and obvious" that Dries Mertens' controversial penalty should not have been given after the holders slipped to defeat at Napoli in their Champions League opener on Tuesday.

The Premier League leaders fell behind in the 82nd minute after Jose Callejon went down easily under pressure from Andy Robertson, before Fernando Llorente's stoppage-time strike secured Napoli a 2-0 win.