Napoli completed a Milanese double with a 3-0 victory at the San Siro as they dismantled a ten-man Inter Milan left searching for answers.
Just two weeks after beating champions AC Milan 3-1 at home, Walter Mazzarri's team took another impressive scalp. Hugo Campagnaro, Christian Maggio and Marek Hamsik scored the goals while Inter's Joel Obi and coach Claudio Ranieri were both shown red.
Napoli fought for the title last season, but missed out as they picked up only one point in four games against their two Milanese Scudetto rivals. However, already this season Napoli have shown they are a different proposition and ahead of Sunday's games, are back on top.
Inter, meanwhile, languish down amongst those at the bottom. With Diego Milito pulling up with a calf problem, Ranieri opted for Giampaolo Pazzini alongside Diego Forlan in attack.
Forlan had the best effort of the first half, dragging a fierce shot just past the upright. Otherwise there were few chances until an explosive incident just before the break.
Obi pushed Maggio as he was storming into the box and the referee pointed to the spot. Obi, already booked for a foul on Ezequiel Lavezzi, was shown a second caution, reducing Inter to ten man just ahead of the break.
With Obi trudging off the pitch, Inter goalkeeper Julio Cesar saved Hamsik's penalty, but Campagnaro was the quickest to the rebound and slammed home at the near post.
That sparked a period of irritation in which Inter captain Javier Zanetti and Cesar were both booked for yelling at the referee, while Ranieri was given his marching orders for doing likewise at the break.
Napoli put the game to bed 11 minutes into the second period when Maggio made another burst from deep and although Japanese full-back Yuto Nagatomo was ahead of him, he hesitated as Cesar came out, allowing the Napoli wing-back to stretch out a leg and lob the goalkeeper.
Juan Zuniga should have added a third from Hamisk's pass, but somehow fluffed the attempt from eight yards with the goal gaping. However, Walter Gargano then played in Hamsik 15 minutes from time and the Slovakian midfielder finished with aplomb.