Independiente and Santos lost their first games of the Copa Libertadores campaign as Boca Juniors drew away from home.
The most successful team in the history of the South American competition with seven titles, Independiente lost 1-0 at Deportivo Lara on Thursday.
Argentine giants Independiente, who last lifted the Libertadores trophy in 1984, succumbed to an 11th-minute strike from Carlos Sierra in Barquisimeto, Venezuela.
Without a win in four matches heading into the opening Group Seven fixture, Deportivo Lara returned to winning ways thanks to Sierra, who found himself unmarked at the back post as he finished powerfully past Independiente goalkeeper Martin Campana.
Santos - three-time champions - also tasted defeat, upstaged by Peruvian hosts Real Garcilaso 2-0.
Gabriel Barbosa - on loan from Serie A giants Inter - had scored three goals in as many games for boyhood club Santos but he was unable to prevent defeat on the road.
Jhonny Vidales broke the deadlock in the eighth minute for Garcilaso before Alfredo Ramua sealed the points with a minute remaining in the Group Six clash.
Carlos Tevez and six-time champions Boca Juniors were held to a goalless draw by Peru's Alianza Lima in Group Eight.
Elsewhere in the group, Bruno Henrique's brace guided Palmeiras to a 3-0 victory over 10-man Junior, while Santa Fe and Emelec drew 1-1 in Group Four.