Napoli rejoined Juventus at the top of Serie A with a 1-0 win at 10-man Sampdoria on Sunday, as the southern club seeks its first Italian title since Diego Maradona first led it to glory.
Edinson Cavani converted a penalty for Napoli in the 67th for his league-best sixth goal of the season after six rounds.
Daniele Guastaldello was given his second yellow card for tripping Marek Hamsik at the edge of the area to set up the penalty.
Replays showed that the penalty may have occurred just outside the area.
"It was on the line, and the line is part of the penalty area," said Napoli manager Walter Mazzarri, who was sent off in the first half for overly vigorous protesting.
Maradona led Napoli to its only two Serie A titles in 1987 and 1990.
At the very least, Napoli is aiming for a top-three finish to get back into the Champions League, having reached the knockout stage last season before being eliminated by eventual champion Chelsea.
Last season, Napoli finished fifth in Serie A.
Against an organized Sampdoria squad, Napoli rarely threatened and was fortunate to come away with a win.
"Last season we would have lost a match like this," Mazzarri said. "We've improved. We're more aware of our capabilities now. The Champions League helped us grow."
Juventus and Napoli have 16 points each, with head-to-head records the first tiebreaker in Italy. Their first meeting comes in three weeks.
Juventus beat Roma and old rival Zdenek Zeman 4-1 on Saturday, while struggling AC Milan gave up a lead in a 1-1 draw at Parma.
Later, Inter Milan was seeking its first home win of the season against in-form Fiorentina, which held Juve scoreless midweek.
Elsewhere Sunday, Lazio beat Siena 2-1 to move into third, four points back.
Newly signed Brazilian midfielder Honorato Ederson gave Lazio the lead with a header in the 17th, and Cristian Ledesma added a penalty in the 38th before Massimo Paci pulled one back for Siena in second-half added time.
Including the Europa League, Lazio had gone three matches without scoring.
Torino thrashed Atalanta 5-1 after Rolando Bianchi scored twice to go with goals from Alessandro Gazzi, Alen Stevanovic and Danilo D'Ambrosio.
Palermo was nearly as impressive, beating Chievo Verona 4-1 with a hat trick from Fabrizio Miccoli for the Sicilian club's first win of the season - and first points since Gian Piero Gasperini replaced the fired Giuseppe Sanino two weeks ago.
Newly promoted Pescara won its second straight with a 2-1 victory at Cagliari's new stadium, which was opened to fans for the first time.
Also, Bologna beat Catania 4-0 with two goals from newly signed Alberto Gilardino.
Earlier in the lunchtime fixture, Udinese and Genoa played to a lackluster 0-0 draw. Udinese manager Francesco Guidolin left top scorer Antonio Di Natale out of his squad for disciplinary reasons and both sides rarely threatened.