Serie A champions Napoli slipped to a shock defeat on Sunday as Monza claimed a deserved 2-0 win against the Partenopei at Stadio Brianteo.
Goals from Dany Mota and Napoli loanee Andrea Petagna handed Luciano Spalletti's men just their fourth top-flight loss of the season, dampening their ongoing title celebrations.
Spalletti opted for a handful of changes against mid-table opposition, and will have expected more from his men despite the low-stakes nature of this clash.
But for Raffaele Palladino, his Biancorossi will nevertheless delight in taking one of the biggest scalps of their successful first campaign in the top flight.
With Napoli already champions and Monza secure in their Serie A place for next season, a lacklustre dead rubber appeared to be on the cards in the first quarter-hour.
But a shrewd counter-attack from the hosts sparked matters into life shortly afterwards, with Mota taking full advantage of a disjointed defence to tuck home the opener.
The visitors chased a response, with Andre-Frank Zambo Anguissa forcing a cracking save from Michele Di Gregorio just before the break, but Napoli were left trailing at the interval.
Matters worsened following the restart, when Petagna darted into the box to seize on a rebound and curl a shot beyond Pierluigi Gollini, finding the bottom-left corner.
Napoli continued to test Monza, but efforts from Mathias Olivera and Khvicha Kvaratskhelia were ably saved, while Victor Osimhen saw a penalty shout waved away.
Napoli's inability to find a way back in saw them suffer a rare reverse, in what fans will hope was merely a hangover from their Scudetto success.