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.

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.

"We gave everything and ran so hard," the Belgium forward told Sky Sport Italia. 

"When you take three points at the end of a game like that, it all feels good.

"It doesn't mean anything to beat the Champions League holders unless we keep going.

"We saw [Group E rivals] Salzburg beat Genk 6-2, they are also a strong team so we have to do well in the next game too.

"Last season we also did well and beat them 1-0 here. I think we prepared well as we knew what we had to do. We didn't have enough of the ball in the first half but we gave our all.

"We lost last season at Salzburg in the Europa League so will not take them for granted. We also have Lecce this weekend and saw that they just beat Torino."

Liverpool captain Jordan Henderson accepts his team must cut out errors at the back, having kept only one clean sheet in eight competitive games this term.

"In the first half I felt we played some good stuff," he told BT Sport. 

"We were just missing that final bit. Napoli are a good side and you have to defend as a team which I felt we did.

"The mistakes for the goal we need to improve on. Overall we can be better, we take responsibility and try and react the right way."