Ranieri's first game in charge on home soil could not have gone any worse as he was banished to the stands to watch his ten-man strugglers humbled in a vital encounter
Claudio Ranieri's home debut as Inter coach ended in embarrassment, as goals from Campagnaro, Maggio and Hamsik gave Napoli a 3-0 victory and extended the Milanese club's shocking home record this season.
Red cards for Joel Obi and Ranieri himself mean the 2010 treble winners are still without a win, or even a goal, in all competitions at San Siro this campaign.
The key news going into the game for Napoli fans was the absence of top-scorer Edison Cavani through injury. Goran Pandev was drafted in as his replacement in an otherwise unchanged side.
For Inter, however, it was the inclusion of Giampaolo Pazzini that was the main surprise. Having been declared injured throughout the week, his inclusion in the starting XI came as a surprise for the home fans.
And it looked as if Ranieri had pulled off a masterstroke on 23 minutes when Pazzini pounced on a spilt ball from De Sanctis to tap in from three yards. Unfortunately for Inter, the striker was judged offside and the goal was, rightly, disallowed.
The match was being played at a frenetic tempo. Both sides were going for broke, but that certainly didn't equal a host of chances. Lavezzi perhaps had the best of them: a cross from Juan Zuniga found the Argentinian, who had his glancing header saved by Julio Cesar on 30 minutes.
The deadlock, however, was broken 40 minutes. A superb run down the right-hand side by Christian Maggio was halted by Joel Obi, who was adjudged to have pushed the central-midfielder inside the box. A penalty was given and a second yellow card brandished to the Nigerian, as Ranieri was subsequently also banished from the contest. The resulting penalty from Marek Hamsik was saved, but Hugo Campagnaro was there to fire in the rebound and give the Partenopei a 1-0 lead at half time.
That man advantage was starting to show after the break, and Christian Maggio reinforced Napoli's dominance on 55 minutes. Hesitation from Nagatomo meant Maggio could nip in 18 yards out, and chip the ball over the on-rushing Julio Cesar to give the visitors a two-goal cushion.
And things got even better for the southerners on 75 minutes. A through ball from Lavezzi dissected the Inter defence, and Hamsik was on hand to calmly slot the ball into the net from 12 yards out.
The win sends Napoli top of the table provisionally on 10 points, whilst Inter languish just outside the drop-zone with just four points to show.