League-leading Benfica won their sixth straight match by beating Gil Vicente 1-0, while rivals Sporting Lisbon won by the same scoreline.
Argentina international midfielder Nicolas Gaitan was the hero at the Estadio da Luz on Sunday, with his 30th-minute strike the difference against cellar-dwelling Gil Vicente.
Gaitan - rumoured to be a January transfer target for Premier League giants Manchester United - was on hand to tuck away the rebound after Maxi Pereira's looping effort hit the post.
Visitors Gil Vicente, who are without a league win in 14 games, ended the match with 10 men following Diogo Viana's dismissal in the third minute of injury time.
Benfica have collected 37 points from 14 games to be six points clear at the summit.
Sporting are 10 points off the pace after winning 1-0 at Nacional.
Carlos Mane struck six minutes into the second half as Sporting extended their unbeaten streak to five matches.
Sporting, though, were forced endure a nervy 13-minute period after Adrien Silva saw red for a second bookable offence in the 77th minute at the Estadio da Madeira.
Elsewhere, Moreirense and Arouca were both 1-0 victors at home.
Moreirense downed Boavista thanks to Andre Simoes' ninth-minute goal, while Arouca had Roberto to thank as they defeated 10-man Maritimo.
Second-bottom Academica and Penafiel played out a 1-1 draw.