Ismael Bennacer scored the only goal of the game as Milan secured a slender Champions League quarter-final advantage over 10-man Napoli with a 1-0 win in Wednesday's first leg.

Just over a week after being thrashed 4-0 by Milan in Serie A, Napoli were the dominant force for large parts at San Siro – only for Bennacer to deal a sucker punch after 40 minutes.

The Algeria international's first Champions League goal proved the difference as Napoli, who had Frank Anguissa dismissed in the second half, were unable to respond without injured star striker Victor Osimhen.

Luciano Spalletti will hope to have Osimhen, and his replacement Giovanni Simeone, back fit for the return leg as Napoli bid to overturn a narrow deficit at home next Tuesday.

Rade Krunic's goal-line block denied Khvicha Kvaratskhelia with the goal gaping after his own errant pass teed up the Georgia winger with less than a minute on the clock.

Anguissa and Piotr Zielinksi both forced smart Mike Maignan saves soon after, before Rafael Leao wasted a glorious chance by dragging Milan's first opportunity wide.

Napoli did not heed that warning, though, as Brahim Diaz exchanged passes with Leao and flicked towards Bennacer, who smashed a left-footed strike past the helpless Alex Meret.

Milan should have doubled their lead on the stroke of half-time but Simon Kjaer headed against the crossbar from Theo Hernandez's corner.

Maignan tipped an Eljif Elmas header onto the crossbar after the interval, though Napoli's comeback hopes were halted with 16 minutes remaining when Anguissa was dismissed for two quickfire yellow cards.

Yet Milan still needed heroics from Maignan, who parried wide from a late Giovanni Di Lorenzo header.

What does it mean? Advantage Milan after profligate Napoli showing

Earlier in the month, Milan handed Napoli their heaviest league defeat since December 2007 and their biggest margin of defeat in a home Serie A game since October 2000.

The Rossoneri's showing here was far less rampant and much more industrious, scoring with their first shot on target after Napoli had nine attempts – three of those testing Maignan – inside the opening 23 minutes.

Milan may not be able to rely on such fortune in the return leg, albeit they will head to Naples with a remarkable record – having lost just one of 10 all-Italian match-ups in Europe (W5 D4).

Brilliant Brahim

Brahim's genius was the key to unlocking the Napoli defence in the first half, spinning to take two players out the game before teeing up Bennacer from Leao's return pass.

That continued Brahim's strong form against Napoli with his third goal involvement when facing the Partenopei – his joint-most against an opponent in all competitions (along with Torino).

Rossoneri rumble Napoli defence again

Napoli have been the dominant force in Italy, and tipped as a European favourite by many, but the Partenopei have been unable to get to grips with Milan's attack this term.

Spalletti's side have conceded six times against Milan in all competitions this campaign, twice as many as they have against any other side (Cremonese, Ajax and Liverpool – all three).

What's next?

Before the return meeting at the Diego Armando Maradona Stadium, Napoli host Verona in Serie A on Saturday – three hours after Milan kick off at Bologna.