Jorge Jesus' men failed to win their first league game of the season for the ninth year in succession as they went down 2-1 to Maritimo at Estadio dos Barreiros.
Derley opened the scoring for the hosts in added time in the first half and, although Rodrigo replied early in the second for Benfica, Sami wrapped up the win in the 78th minute.
The hosts held a deserved half-time lead courtesy of Rafael Martins' 14th-minute goal, but the game would descend into controversy early in the second period.
Porto were correctly awarded a penalty that Josue converted in the 49th minute, but Vitoria goalkeeper Pawel Kieszek would take exception to the midfielder's attempts to retrieve the ball and subsequently saw red after attempting to land a headbutt.
Paulo Fonseca's team made the most of their one-man advantage from that point on, as goals from Juan Quintero and Jackson Martinez wrapped up a routine win.
And Gil Vicente beat Academica 2-0 at Estadio Cidade de Barcelos with Bruno Moraes converting a sixth-minute penalty and Luis Martins calming home supporters' nerves in the fourth minute of added time.
