River Plate and Gremio claimed first-leg wins against Guarani and Godoy Cruz respectively in the last-16 of the Copa Libertadores.
On Tuesday, 2015 champions River triumphed 2-0 at Paraguayan hosts Guarani in the first knockout round of South America's premier club competition.
River - Group 3 winners - were too good in Asuncion as Ignacio Scocco and Marcelo Larrondo gave the Argentine giants a commanding lead.
Scocco made the breakthrough eight minutes before half-time when his free-kick took a wicked deflection and rolled beyond Guarani goalkeeper Alfredo Aguilar.
River sealed the win with two minutes of regulation time remaining after Larrondo glanced a close-range header past Aguilar for Marcelo Gallardo's men.
Gremio will take a one-goal cushion back to Brazil after edging Godoy Cruz 1-0 in Mendoza.
Renato Portaluppi's Gremio advanced to the knockout round as Group 8 winners, while Argentine hosts Godoy Cruz finished runners-up to Atletico Mineiro in Group 6.
And two-time competition winners Gremio came out on top in the first leg thanks to the fastest away goal in the Libertadores play-offs.
Ramiro opened the scoring after only 44 seconds, tucking the ball underneath Godoy Cruz keeper Rodrigo Rey at Estadio Malvinas Argentinas.