Antoine Griezmann's first away Champions League goal since February 2017 ensured Barcelona secured a hard-fought 1-1 draw in the first leg of their last-16 tie with Napoli at the San Paolo.
Dries Mertens brilliantly equalled a club record in the first half with his 121st strike for Napoli (30), but after the Belgian was forced off injured early in the second period, Barcelona asserted themselves, and duly levelled when Griezmann crashed home from Nelson Semedo's cross (57).
Jose Callejon had a glorious chance to restore Napoli's lead when put through by substitute Arkadiusz Milik but Marc-Andre ter Stegen made a vital save.
Arturo Vidal was dismissed for two quickfire yellow cards as a result of the same incident as he clashed with Mario Rui (89), but Barcelona will seek to protect their away goal when these two sides meet again for the second leg on March 18 at the Nou Camp.
Napoli: Ospina (6), Di Lorenzo (6), Manolas (7), Maksimovic (7), Rui (6), Fabian (7), Demme (7), Zielinski (6), Callejon (6), Mertens (7), Insigne (6).
Subs: Allan (6), Politano (5), Milik (6).
Barcelona: Ter Stegen (7), Nelson Semedo (7), Pique (6), Umtiti (6), Firpo (6), Busquets (8), Rakitic (5), de Jong (6), Vidal (5), Messi (7), Griezmann (7).
Subs: Arthur (6), Lenglet (n/a), Fati (n/a).
Man of the match: Sergio Busquets.
How Neapolitan delight turned to despair
Napoli were eliminated in their two previous European Cup two-legged ties with Spanish opposition, both times against Real Madrid, but Gennaro Gattuso's side came up with the perfect game plan to try and provide them with a slender advantage heading to the Nou Camp in three weeks' time.
The Napoli boss, who won the competition on two occasions as a player with AC Milan, set up his team to defend in a compact shape before counter-attacking at pace.
In the temple of Diego Maradona, Lionel Messi recorded the lowest pass completion of any Barcelona player during the opening 45 minutes - just 75.7 per cent. The Argentine was desperate to impress at the San Paolo, where his compatriot Maradona had made such an impact during his glittering career, but he was well-marshalled during the opening period.
Kalidou Koulibaly remained sidelined for Napoli meaning Nikola Maksimovic continued to deputise in defence. Arkadiusz Milik was named on the bench as he continues to battle back to full fitness.
Samuel Umtiti was preferred by Quique Setien to Clement Lenglet in Barcelona's back line while Arturo Vidal started in place of Ansu Fati.
Napoli's tactics were paying off - and they duly broke the deadlock in spectacular fashion. Piotr Zielinski took advantage of a poor touch from Junior Firpo to collect his own pass before the Polish midfielder picked out Mertens to the left of Barcelona's penalty area.
The Belgian wasted little time in stepping inside Nelson Semedo before unleashing an unstoppable strike into the top corner beyond Ter Stegen for his milestone goal for Napoli. It meant the Italian side extended their impressive record of only failing to score once in 21 Champions League games at home, a goalless draw against Dynamo Kiev in November 2016.
But Mertens was forced off just eight minutes into the second period after a robust challenge from Sergio Busquets. Referee Felix Brych brandished only a yellow card, which will rule Spain's World Cup winner out of the second leg - but he would go on to play a vital role in the equaliser.
Barcelona had failed to register a shot on target when Busquets found the run of Semedo beyond Mario Rui down the right, and the full-back's cross was fired home first time by Griezmann.
The Catalan giants sensed a first away win against Italian opposition in the Champions League knockout stages since April 2006 - against an AC Milan side containing Gattuso - but instead, it was Napoli who very nearly regained the advantage.
Five minutes after Griezmann's leveller, Milik found Callejon in space to his right after Napoli had been successful with their high press, but the former Real Madrid winger could only fire his shot straight at Ter Stegen.
Samuel Umtiti had Barcelona's best chance of taking a lead back to the Nou Camp as he rose to head Messi's corner over as the Argentine's influence began to grow.
Barcelona head coach Quique Setien will be without Busquets and Vidal for the second leg, after the Chilean lost his cool in the final stages, first cautioned for catching Rui before receiving his marching orders for leaning his head into the Napoli full-back during the ensuing heated confrontation.
But having progressed past the Champions League round of 16 in each of the last 12 seasons, Barcelona will be confident of completing the job at the Nou Camp next month.
Man of the match - Sergio Busquets
Sergio Busquets had just collected his award as the official man of the match when he stood reflecting on the ramifications of Vidal's late red card. The red mist had descended on the Chilean moments before Gerard Pique was forced off after rolling his ankle, making him a doubt for the forthcoming clash with Real Madrid on Sunday.
Busquets - who made a game-high 121 passes including 86 into the opposition half - said: "We had the Vidal sending off, and then what happened to Pique. Hopefully it's nothing but we have to face up to it. We don't have a very big team - unfortunately, the planning has been like this."
86 - Sergio Busquets have attempted 86 passes in opposite half vs Napoli, more than any other single #UCL game away from home in his career, except vs Chelsea in April 2018 at Stamford Bridge (90). MVP@FCBarcelona #ChampionsLeague #NapolesBarca pic.twitter.com/zSQym00m8u— OptaJose (@OptaJose) February 25, 2020
It was a throwaway remark at the end of a full-blooded contest but it also spoke volumes for how the once-great Barcelona team that heralded the start of the old decade is now searching for its identity.
Busquets has been the midfield metronome for Barcelona for these past 10 years, but on this evidence, he is still head and shoulders above those in his position.
He will, of course, be absent for the second leg after he was booked for a crunching challenge on Mertens. Having effectively eradicated Napoli's chief threat and then played a part in Barcelona's equaliser, it was job done.
What the managers said
Barcelona coach Quique Setien: "It's a positive result for us overall. We controlled most of the game, but we lacked something in the final third against such an organised defence by Napoli.
"After the equaliser, they opened up a little and we were able to hurt them more. They played very well and it was not easy, so a score draw is fine going into the second leg.
"We will have more options in the second leg, as it is unlikely a team will be able to defend for that long at Camp Nou. So we have got to think positive and cannot complain.
"A yellow card for the foul is one thing, but the second is too much. There are moments of tension that players who experience the game with his temperament can have."
Napoli coach Gennaro Gattuso: "Barcelona struggled because we were very careful. We did well as a team to play together like this. I am disappointed because we made one mistake and they made the most of it.
"We suffered tonight, tactically we were almost perfect, but we could have done better and been more clinical.
"Our dream at the Nou Camp is to play further up the pitch. It's not over - it will be difficult, but we'll go there and try to progress."
- Barcelona have progressed from each of their last 19 knockout ties in the Champions League after avoiding defeat away from home in the first leg.
- Since winning their first ever game in the Champions League knockout stages (3-1 v Chelsea in 2011-12), Napoli have failed to win any of their last four games outside of the group stage (D1 L3), with three of those coming against Spanish opponents.
- Barcelona have only won one of their previous nine away games in the Champions League knockout stages (D3 L5), with that lone victory coming against Manchester United in April 2019.
- Gennaro Gattuso and Quique Setien took charge of their first Champions League games tonight - it is the first time in Champions League history that two managers are facing in the knockout stages in their first ever games in the competition.
Napoli return to domestic action this weekend as they host Torino on Saturday in Serie A; kick-off at 7.45pm. Meanwhile, Barcelona visit Real Madrid on Sunday at 8pm - follow El Clasico on Sky Sports' digital platforms with our dedicated live blog from 6.45pm.
The return leg between Napoli and Barcelona takes place at the Nou Camp on March 18 at 8pm.