Copa Libertadores runners-up Boca Juniors clinched a vital 1-0 win over Uruguayans Nacional to maintain their chances alive in the Group One.
Carlos Bianchi's squad did not start well as defender Claudio Perez earned an early bath in the 21st minute after he axed down Juan Albin inside the box. However, forward Ivan Alonso missed from the spot.
Just before the break playmaker Juan Roman Riquelme did not miss his chance from the spot and that proved to be the winner.
Boca midfielder Ribair Rodriguez said: "It was a hard game, but we had a lot of confidence. We managed to control their attack when they come with all their strength to get an equaliser. This result put us on track to go for the cup."
After four games, Nacional remain top with seven points, one ahead of Boca.
In Group Three, Argentineans Arsenal Sarandi earned a last-gasp 2-1 victory against Brazilian giants Sao Paulo.
Home midfielder Jorge Ortiz broke the deadlock after he found a loose ball inside the box and beat goalkeeper Rogerio Ceni near the hour mark.
Sao Paulo netted the equaliser after striker Aloisio headed home a rebound off goalkeeper Cristian Campestrini.
With five minutes to go, defender Diego Braghieri's superb volley from outside the box made the Julio Grondona stadium explode.
"It was a nice goal," he said. "We are very happy as we could beat a great team. We knew that we could win it as they left space to attack. Now, we have to think ahead as qualification is still a long way off."
Finally, Bolivian side San Jose saw off Colombians Millonarios 2-0 to grab their first triumph in the Group Five.