A back-and-forth match was eventually settled by Poland striker Robert Lewandowski’s close-range finish with seven minutes remaining in normal time.
Following a fast start, Barcelona delivered a devastating one-two punch to Napoli with two goals in three minutes.
First, 20-year-old midfielder Lopez capitalized on his chance to impress on the big stage, scoring with a side-footed goal 15 minutes after Lewandowski dummied Raphinha’s low cross.
Raphinha, a former Leeds winger, also played a role in Barcelona’s second goal, leading a counter-attack and looping a shot off the post before Manchester City loanee Cancelo scored off the rebound.
Barcelona, on the other hand, lost impetus, and Napoli equalized on the half-hour mark when Kosovan centre-back Rrahmani advanced to slot past Marc-Andre ter Stegen after a cutback from the right.
Napoli pressed hard for an equaliser, but squandered their finest chance with 10 minutes left when Jesper Lindstrom fired a free header wide from seven yards.
However, they fell short as Barcelona won for the first time in five Champions League knockout games when Lewandowski tapped home following clever play from Sergi Roberto.