After losing just once in 30 league games last season, Benfica has already matched that total this term, suffering a 2-1 defeat at Maritimo on Sunday.
The home side grabbed the lead in first-half stoppage time through a penalty kick from Derley, while Benfica was back on level terms in the 51st minute courtesy of a goal from Rodrigo.
But instead of pressing on and claiming three points like it did so many times last season, Benfica watched as Leocisio Sami tallied the winning goal 12 minutes from time for Maritimo, handing the home side a massive three points to begin the year.
Making matters worse for Benfica was the fact that defending champions FC Porto rallied to score three times in the second half of a 3-1 victory at Setubal.
Rafael Martins put Setubal in front after 14 minutes, but things came apart for the hosts after halftime when Pawel Kieszek was sent off in the 49th minute as Josue scored the equalizer from the penalty spot for Porto.
From there, Porto made the most of its numerical advantage as Juan Quintero put the visitors ahead in the 61st before Jackson Martinez netted an insurance tally two minutes from time.
Sporting Lisbon got off to an emphatic start with a 5-1 win over Arouca as Fredy Montero scored a hat trick, Rio Ave claimed a 3-0 win at Belenenses, while Sunday's other match saw Gil Vicente down Academica, 2-0, with goals from Bruno Moraes and Luis Martins.
Braga opened the campaign on Friday with a 2-0 win at Pacos Ferreira courtesy of goals from Paulo Vinicius and Felipe Pardo, Evandro scored twice to help Estoril top Nacional, 3-1, and Guimaraes got a pair of second-half goals from Ouwo Maazou in a 2-0 triumph over Olhanense.