Juventus missed the chance to reclaim an eight-point lead at the top of Serie A after suffering a shock home defeat to 10-man Sampdoria.
Having finished 2012 with a record haul of 94 points, Juve boss Antonio Conte was backing a concerted bid to outstrip that achievement this year, and Sebastian Giovinco's early penalty put his side on the right path.
Juve's task looked easier when Gaetano Berardi saw red for two first-half bookings but the numerical advantage did little to help the hosts, as Mauro Icardi levelled the scores shortly after the break.
Icardi completed his brace with what proved to be the winner, his sensational strike rattling the Bianconeri to condemn them to a second home defeat of the season, also earning Delio Rossi a first victory as Samp boss.
And with second-placed Lazio beating Cagliari last night, Juventus now lead the standings by just five points ahead of a daunting trip to Parma.
Within minutes, Giovinco had a fine opportunity to kickstart Juventus' bid for a record-breaking 2013, firing narrowly wide from Simone Padoin's pinpoint cross.
But home debutant Federico Peluso, recently signed from Atalanta, saw his blushes spared by goalkeeper Gianluigi Buffon as Andrea Poli twisted past him with ease.
Giovinco wriggled into good space once again, this time tapping the ball tamely against Sergio Romero on the turn, but the diminutive forward would make the breakthrough moments later.
Berardi up-ended Claudio Marchisio to earn his first yellow card of the day in the 24th minute and Giovinco coolly beat Romero from the spot.
Berardi soon received his second booking and his marching orders for a late tackle on Leonardo Bonucci and Samp were seemingly up against it.
Alessandro Matri's appeals for a second penalty fell on deaf ears, though, and the visitors were not out of contention just yet.
And seven minutes after the break, Samp were level.
Buffon was clearly at fault as Icardi attempted a straightforward punt on his left foot, with the ball sailing into the back of the net.
Andrea Barzagli's ambitious effort from outside the box was lacking accuracy and Samp were starting to look the more inspired side.
If Italy's veteran goalkeeper had been found wanting for Icardi's first goal, he could not be blamed for a screamer from the young striker as the Genoa side claimed a shock lead in the 69th minute.
Four minutes later, Mirko Vucinic rattled the crossbar before teeing up fellow substitute Fabio Quagliarella for an easy chance, which sailed wide.
With all three of Juve's replacements in action, the Italian champions were temporarily reduced to 10 men when Marchisio was forced onto the sidelines through injury in the 78th minute.
In a rare display of insecurity from the league leaders, Juve retreated into their own half as time ticked away, with Marchisio's brief return not enough to salvage a point for Conte's men.