Newell's Old Boys opened their Torneo Apertura campaign with a 1-0 win away to Boca Juniors on Sunday.
Mauricio Tevez scored the only goal just before half-time to give Gustavo Raggio's side all three points against the side second in last season's championship.
Independiente also made a winning start, beating Atletico Rafaela 3-0.
Federico Mancuello broke the deadlock in the 44th minute and second-half goals from Francisco Pizzini, two minutes after coming on as a substitute, and Juan Lucero secured the points.
Gimnasia La Plata and River Plate drew 1-1, with both goals remarkably coming in stoppage time at the end of the game. Teofilo Gutierrez appeared to have won it for River only for Pablo Vegetti to equalise.