The two sides met in the group stages of the competition last season with Napoli winning 1-0 in Italy and Liverpool winning 1-0 in England.
That clash at Anfield was the sixth and final match of the group, with Liverpool needing to win 1-0 or by two clear goals.
They did that by the skin of their teeth - Mohamed Salah’s strike and Alisson’s wonder save in injury-time making sure they would progress to the knockout round.
Of course, we all know they went all the way and claimed their sixth European Cup in Madrid.
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And in tonight's clash, Napoli ran out 1-0 winners once again.
It looked as though both defences would come out on top as the match edged towards a 0-0 draw.
That was until Andy Robertson appeared to bring down Jose Callejon in the penalty area with less than 10 minutes remaining.
However, replays showed that Callejon was already on his way down before he made contact with Robertson.
Despite that, VAR didn't overrule the original decision and Mertens stepped up to give Napoli the lead.
Substitute Fernando Llorente - who played in last season's Champions League final for Spurs - then sealed the win in injury-time.
Both sides are still expected to progress through the group.
However, RB Salzburg have taken command of the group after their incredible 6-2 victory over Genk.
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