Dries Mertens told Napoli they must back up their 2-0 victory over Liverpool in Tuesday's Champions League opener.
For the second season in a row Jurgen Klopp's Reds were beaten at the Stadio San Paolo without scoring a goal.
But last time out the Partenopei failed to qualify from the group stage despite having earned a 1-0 home victory over Liverpool, who went on to win the tournament.
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Mertens' penalty gave Napoli a late lead and Virgil van Dijk's rare error ensured former Tottenham striker Fernando Llorente could add a second to settle matters.