Born in Paderno Dugnano, in the province of Milan, Napoli started his career at Pro Sesto of Serie C1.
He was signed by Internazionale Primavera in a co-ownership deal in January 2007, for a fee of about €70,000[2] (in part-player swap: Marco Dalla Costa and Daniele Federici), but was loaned back to Pro Sesto for the second half of the 2006–2007 season.
[5] In July 2009, along with Primavera team-mate Cristian Daminuţă and Enrico Alfonso, they were loaned to Serie B side Modena.
In July 2011 he was sold to Serie B newcomer Juve Stabia on a co-ownership deal, joining former teammate Cristiano Biraghi.
In January 2012 he joined Prato on loan in Lega Pro Prima Divisione and he scored the decisive goal in the play-off against Piacenza.