Late goals from Ivan Furios and Jose Adolfo Valencia gave 10-man Olimpo a 2-0 win over Lanus on Sunday.
Olimpo were hampered by Pablo Luguercio's 15th-minute but kept the visitors at bay.
And despite their numerical disadvantage, they took the lead through Furios in the 83rd minute and secured the points when Valencia added a second in the closing moments.
Estudiantes missed the chance to go top of the table but still rose to third place with a goalless draw against Newell's Old Boys.
Goals from Sebastian Romero and Teofilo Gutierrez gave Quilmes and River Plate 1-0 wins over Tigre and San Lorenzo respectively.