Ciro Immobile scored twice as Lazio cast some early doubt on Juventus' ability to sustain their domination of Italian football by claiming a 3-2 victory in the Supercoppa Italiana in Rome.
Juve -- under Antonio Conte and then Massimiliano Allegri -- have won Serie A six years in a row, reaching the Champions League final twice in that period and winning the Coppa Italia three times.
But the shock sale of long-serving defender Leonardo Bonucci, coupled with uninspiring recruitment in the transfer window, has created suspicion that the Old Lady's star might be about to fade.
Lazio certainly proved that Juve have work to do before the new league season starts next weekend, with Immobile scoring a penalty before cutting through a soft back-line to double his tally.
Paulo Dybala launched a one-man comeback at the death, steering home a free-kick with five minutes remaining before converting a spot-kick, but Alessandro Murgia rescued the cup for Lazio.
This preseason triumph also served as prompt revenge for the Bianconeri, who lost the Coppa Italia final to Juve back in May.
Juve, who were beaten 4-1 by Real Madrid in their last competitive outing, June's European Cup final in Cardiff, started positively and Juan Cuadrado was denied an early tap-in by Thomas Strakosha.
Gonzalo Higuain got the Lazio goalkeeper working again with a speculative shot and, in the eighth minute, Strakosha rushed out to snatch the ball away from the onrushing Mario Mandzukic.
Lazio did not seem fazed and steadily grew into the game, with Gianluigi Buffon forced to collect a couple of tricky deliveries from Marco Parolo and Luis Alberto.
In the 31st minute Lazio won a penalty when Buffon fouled Immobile in the Juve box and the veteran stopper could not keep out his Italy team-mate's carefully placed spot-kick.
The Bianconeri looked rattled and needed Buffon to make a smart double stop on Dusan Basta and then Lazio's summer signing Lucas Leiva to keep the scoreline respectable heading into the break.
Juve's nerves did not settle during the interval and Buffon was soon picking the ball out of his net for a second time. Nine minutes after the restart, Immobile beat the 39-year-old with an agile header.
There was a good opportunity to halve the deficit when Dybala won a free-kick within shooting range, but Miralem Pjanic's attempt sailed over Strakosha's bar.
Substitute Douglas Costa, a loan capture from Bayern Munich, dragged a save out of Strakosha in the 68th minute and it was not long before he teed up Higuain for an effort at the far post.
With time running away from the Bianconeri, they finally grabbed a goal, with Dybala spinning the ball over the wall and home from a free-kick following a foul by Parolo.
The Argentinian forward looked to have forced extra-time when he slotted past Strakosha from the spot to punish Adam Marusic for impeding Alex Sandro, but a further minute into stoppage time Lazio replacement Murgia salvaged the win with a cool right-footed finish.