A serious-looking injury to Luca Antonelli marred a difficult game for AC Milan as they were beaten 1-0 by Udinese on Sunday.
Stipe Perica struck in the 88th minute to snatch all three points for the visitors and end a run of nine away games against Milan without a win.
Vincenzo Montella's side were looking to bounce back from a 4-2 loss to Napoli last month, but were unable to test Orestis Karnezis in the Udinese goal sufficiently despite dominating possession at a stifling San Siro.
A disappointing result was marred by a worrying moment involving Antonelli, who was carried off following lengthy treatment on the pitch after he took a hit at a corner.
Jose Sosa came closest for Milan, striking the crossbar from 18 yards, but they struggled to fashion service for Carlos Bacca against a disciplined visiting defence.
Milan pushed to the end, but were hit with a sucker-punch on the break when Perica turned in a cross from Emmanuel Badu - who was a little fortunate to be on the pitch - meaning Udinese leapfrog Montella's side in the Serie A table and sit on six points from three games.
Neither of these teams has looked solid defensively in the opening weeks of the season, but goalscoring chances were few and far between in an even opening half-hour.
Gianluigi Donnarumma got down well to deny Cyril Thereau after a promising Udinese counter, before the officials sanctioned a water break due to the sweltering conditions inside San Siro.
Sosa left the crossbar shaking with a fine volley from the edge of the area, but Udinese held firm against mounting Milan pressure as the first half wore on.
Milan were keen to keep up their attack after half-time, but understandably lost some momentum when Antonelli, following several minutes of treatment, was carried off on a stretcher wearing a neck brace after an accidental collision at a corner.
Badu was perhaps fortunate to escape with just a yellow card after catching Sosa with a raised arm, and the home fans made their growing frustrations clear when Emil Hallfredsson almost snatched the lead for Udinese, flashing a shot wide of Donnarumma's left-hand post from close range.
Giacomo Bonaventura finally brought a save from Karnezis on 67 minutes - though it was a simple enough stop from a header - before Bacca hit the side-netting with his first half-chance of the match after linking up well with Suso.
Milan kept up the pressure but their attacking endeavour began to wilt in the heat in the closing stages, and San Siro was stunned when Badu's floated cross from the right was steered into the bottom corner by Perica via a heavy deflection off Ignazio Abate, allowing Udinese to claim the win.