River Plate coach Marcelo Gallardo believes the two-time Copa Libertadores champions are reaping the rewards of his squad rotation.
Gallardo's men boast a two-goal lead as they prepare to travel to Paraguay for Tuesday's semi-final return leg against Guarani.
River's victory in the Argentine capital ended a run of four matches without a win and Gallardo feels the club's first-leg triumph was boosted by his changes, having experimented with the likes of Mercado, Eder Alvarez, Sebastian Driussi, Lucas Boye, Augusto Solari, Julio Chiarini, Javier Saviola, Fernando Cavenaghi and Emanuel Mammana among others over recent weeks.
"River is prepared to play this type of game. This confidence, this security makes me have no more doubts about changes [in the line-up]," said Gallardo, who has since lost Colombia international Teo Gutierrez to Sporting Lisbon and oversaw a 5-1 win at Atletico Rafaela on Saturday.
"During the Copa America players came and went, but our goal has always been to reach the last four playing in the best way.
"Some people wanted to generate controversy, create doubt, but we know that this type of match [against Guarani] needed."
Fernando Jubero's Guarani have tasted back-to-back league defeats at Estadio Rogelio Lorenzo Livieres, falling to Sportivo San Lorenzo and Olimpia.
"We must be proud of the team, as they left skin and fought hard," Jubero said following the first leg.
Guarani have never reached the final of South America's premier club tournament.
