Pacos de Ferreira extended their unbeaten run to four games with a 1-0 victory over Gil Vicente in Liga Sagres on Friday.
Vitorino Antunes' 77th-minute goal proved the difference as Pacos climbed to fourth on the table with their third win of the season.
But Pacos, on 14 points, could slip as low as sixth place depending on other results at the weekend.
Gil Vicente battled fiercely in search of an equaliser at home, but failed to salvage a point and slumped to their third straight loss. Paulo Alves' men are in ninth place, but just two points above the relegation zone after nine games.