Velez Sarsfield missed the chance to go to the top of Argentina's Apertura as they were held to a goalless draw by Gimnasia La Plata.
Gimnasia lie one place off the foot of the table - but their defence held firm to deny El Fortin the three points which would have moved them above Estudiantes in the standings.
Boca Juniors moved into the top half with a 2-1 defeat of third-placed Arsenal Sarandi.
Substitute Sergio Araujo gave Boca a 27th-minute lead and although Lisandro Lopez levelled three minutes into the second half, Martin Palermo won it for the hosts 15 minutes from time.
River Plate could not find the victory which would have moved them into the top five as they were held to a goalless draw at San Lorenzo.
In the other match, Racing Club drew 1-1 at home to bottom club Quilmes, with Francisco Cerro giving the strugglers a 69th-minute lead, only for Gabriel Hauche to equalise two minutes later.