AC Milan fell to their third successive group stage defeat on their return to the Champions League with a 1-0 loss away to FC Porto.
A controversial goal from Luis Diaz is all that separated the sides at the Estadio do Dragao, and Stefano Pioli's men have a mountain to climb if they're to reach the knockout stages.
Diaz nearly gave Porto a fifth-minute lead when his strike thundered against the woodwork, while Mehdi Taremi particularly put the frighteners on Milan's weakened backline.
Olivier Giroud and Simon Kjaer both failed to beat Diogo Costa with headers as a toothless Milan struggled to trouble their hosts.
Colombia international Diaz finally gave Porto a deserved lead after 65 minutes when the Rossoneri failed to deal with a Joao Mario cross. Taremi managed to lay the ball off to Diaz to slot it home, but Milan were furious that the striker was deemed not to have fouled Ismael Bennacer in doing so.
