AC Milan were shown up by Sampdoria at the Stadio Luigi Ferraris on Sunday and beaten 2-0 by the hosts, throwing up question marks over the legitimacy of their title credentials.
It was a lively start to the game as sub-par Milan were penalised with a penalty for a handball by Franck Kessie in the box. It seemed like a harsh call from the TV replays for audiences at home, but moments later the referee consulted the VAR system to overrule his original call.
The decision took far less time than has been seen in other matches over the past few months since its inception, and the correct call was reached and the penalty was waved away - the ball had struck Kessie's arm down by his side and not the one that was raised.
Still, the trend continued and it was Sampdoria who took the game to Milan, and the best chance of the first half went the way of Duvan Zapata. The man signed from Napoli in the summer proved a real handful for the Milan backline and particularly for his cousin Christian Zapata throughout the game - on 12 minutes he headed a Fabio Quagliarella cross across Gianluigi Donnarumma, but the teenager was well positioned to be able to dive to catch it.
A few moments later he might have opened the scoring but could only glance a header wide from a corner, when he really ought to have scored.
Milan, sloppy in their passing, continued to invite the hosts forward and Zapata might have done better with another chance on 36 minutes after good initial dribbling from the left side - his cut back was well worked but the finish did little to trouble Donnarumma.
Midfielder Lucas Torreira went close just before the halftime whistle after the ball dropped to him on the edge of the Milan box. A fake shot allowed him to dribble closer but the Uruguayan shot just wide.
The second half yielded a lot of similar patterns to that of the first - Sampdoria denying Milan any sort of rhythm in their passing and trying to capitalise on a lot of sloppy play.
In the 53rd minute, Quagliarella had arguably the game's best chance when he found himself in the clear down the right of the Sampdoria penalty box. The former Juventus man - who has only ever scored once against the Rossoneri in 20 appearances - shot well wide though.
Milan only started to grow in to the game from the hour mark onward, and Kessie made a burst into the box after nice work from Suso, only to lose his balance under pressure at the vital moment.
Moments later, Nikola Kalinic skied a good opportunity from around eight yards out after a good low cross from Ricardo Rodriguez after some tight marking from Gabriel Ferrari.
The scoring was opened on 71 minutes after some downright comical defending from Christian Zapata, which allowed his cousin Dusan to lash home from close range for Sampdoria. The defender tried to head the ball out away from danger and failed to generate any power on the ball, leaving him with egg on his face.
Vincenzo Montella brought on Hakan Calhanoglu, Patrick Cutrone and Fabio Borini but the trio failed to have any kind of impact for a disappointing Milan.
Sampdoria made sure of all three points in the 90th minute, when man-of-the-match Duvan Zapata played through substitute Ricky Alvarez, who finished cooly across Donnarumma with his left foot.
The manner of the defeat might just bring back one or two Milan fans who had title expectations down to earth - the club find themselves six points adrift of Napoli and Juventus, who look far more incisive at this early point in the season.
Sampdoria now find themselves a point behind Milan in sixth, and remain unbeaten in the league having looked quietly impressive so far.