Gustavo Morinigo's Nacional Asuncion and San Lorenzo put themselves on track for the semi-finals of South America's premier club competition with 1-0 victories against Arsenal and Cruzeiro respectively in their opening legs.
Nacional Asuncion had edged Velez Sarsfield en route to the last eight and the Estadio Defensores del Chaco played host to Argentinean opposition yet again on Wednesday.
It proved to be a successful night for the Paraguayan giants, who will take a slender lead into the return leg thanks to Derlis Orue's 36th-minute effort, which ended the team's run of back-to-back draws.
San Lorenzo extended their unbeaten run to seven games in all competitions following Santiago Gentiletti's second-half header.
The opening 45 minutes failed to produce a goal but the home side's towering defender was on hand to guide his header past Fabio just after the hour-mark as Cruzeiro slumped to their first defeat in 13 games.
