Lisbon - FC Porto stumbled to a 1-0 loss at Maritimo on Sunday, giving Benfica the chance to increase its lead of the Portuguese league.
Benfica leads Porto by six points before it visits Pacos Ferreira on Monday.
Bruno Gallo scored what proved to be Maritimo's winner with a left-footed volley in the 32nd minute.
Porto's Cristian Tello hit the post in the 63rd, while Maritimo goalkeeper Romain Salin saved several shots.
Porto played the final 13 minutes with 10 men after center back Raul received his second booking.
Sporting Lisbon closed to within one point of Porto after beating Academica 1-0.