Santos leapfrogged Estudiantes as they continued their winning run in the Copa Libertadores, while River Plate played out another draw.
Arthur Gomes was the hero for Brazilian visitors Santos, who moved top of Group Six with a 1-0 victory at Estudiantes on Thursday.
It was not the cleanest of goals but Gomes was on hand to bundle the ball over on the goal line after Eduardo Sasha's effort hit the post in Buenos Aires.
The win saw Santos moved two points ahead of Argentine rivals Estudiantes in the group standings.
Argentine giants River are still searching for their first win of the campaign following a goalless draw against Santa Fe in Group Four.
River drew 2-2 with Flamengo on matchday one and they were forced to share the spoils again – this time at home to Colombia's Santa Fe in the Argentinian capital.
Delfin won for the first time in three games, accounting for Colo-Colo 2-0 in Group Two, while leaders Atletico Nacional lost away to Bolivar.