Holders Liverpool lost 2-0 at Napoli in their Group E Champions League opener on Tuesday night to become the first defending champions to lose an opening game since AC Milan did in 1994.
Dries Mertens’ penalty and a late contribution from Fernando Llorente condemned the Reds to defeat.
The Belgium forward converted the spot kick after Liverpool defender Andy Robertson was judged to have fouled Jose Callejon.
Former Tottenham forward Llorente then capitalised on a mistake from Virgil van Dijk in stoppage-time to roll the ball past Adrian.
Adrian had earlier made two vital saves for Liverpool, who initially struggled to impose themselves in the intimidating atmosphere of the San Paolo Stadium.