Newly-promoted Atletico Rafaela are top of the Apertura standings after winning 1-0 away to Union Santa Fe on Sunday.

Atletico, the 2010/11 second-tier champions, made it four wins from five games in the top flight as Juan Pablo Cardenas' 17th-minute own goal proved decisive. Cardenas' day was to get even worse, as he was sent off with three minutes to go as Union slipped to their second defeat of the campaign.

Buenos Aires giants Boca Juniors are just a point behind Atletico following a 1-0 win away to Independiente which was secured by Rolando Schiavi's 49th-minute goal.

Olimpo claimed their first Apertura victory, beating 2011 Clausura champions Velez Sarsfield 2-1. Martin Rolle put Olimpo in front in the 10th minute before veteran forward Guillermo Franco drew Velez level (39). The winner came with 20 minutes to go for Olimpo and was scored by Nestor Bareiro.

Sunday's other match between San Martin San Juan and Argentinos Juniors finished goalless.