Cagliari certainly came out fighting against Milan, with Ze Pedro picking up a yellow card in the opening two minutes.
The Rossoneri soon punished their visitors, too, as Alexis Saelemaekers stole into the area after a brilliant assist from Santiago Gimenez and fired low past Elia Caprile.
Milan were quite happy to cede possession to Cagliari in the opening stages, and had Alessandro Deiola’s effort not gone high and wide, the visitors could’ve quickly been on level terms.
Mike Maignan then had to fly to his left and acrobatically push Gianluca Gaetano’s effort wide; however, from the resulting corner, Yerry Mina’s knockdown was slammed home by Gennaro Borrelli for the equaliser.
As the half reached the 30-minute mark, it was the hosts in the ascendancy, though both Christopher Nkunku and Youssouf Fofana’s on-target efforts failed to trouble Caprile.
With Milan needing a victory to guarantee Champions League football next season, their urgency was notable, though their finishing was regrettable.
Christian Pulisic came on for Gimenez at the break to make his 100th Serie A appearance, as Milan attempted to take the game to their opponents.
Once again, however, Cagliari stunned the San Siro when Juan Rodriguez headed home his first of the season after a free-kick confused the hosts’ defence.
That goal arrived despite over 40% of the action having taken place in Cagliari’s own defensive third.
Max Allegri’s response was to immediately send on Luka Modric, Niklas Fullkrug and Zachary Athekame, but far from having the required impact, it appeared to derail Milan’s attacking intentions and, in fact, Cagliari continued to pour forward, with all of Gaetano, Borelli, Gabriele Zappa, Ibrahim Sulemana, Sebastiano Esposito and Michel Adopa having efforts at goal.
Man-of-the-match Maignan stopped the scoreline from being even more embarrassing for Milan with an incredible stop late on from a clean-through Paul Mendy.
The result saw the Rossoneri unable to make it an eighth final-day win in the last nine seasons, and unable to qualify for the Champions League, whilst Cagliari’s victory was just their second in the last 43 H2H games (D10, L3). It also meant that the Sardinian side ended the 2025/26 campaign by snapping their six-match winless run on the road.