Uruguayan giants Nacional claimed a surprise win at La Bombonera as they beat Boca Juniors 1-0 in Buenos Aires to take sole lead in the Copa Libertadores Group 1 on Thursday.
Andres Scotti, with a header from a corner, netted the winner after 20 minutes as Nacional moved on to seven points in the standings, three more than Mexico's Toluca.
Nacional defender Alejandro Lembo was sent off in the second half after protesting to the referee.
Boca Juniors, who missed some opportunities to equalise in the second half, remain third on the points, with three games to play.
Nacional midfielder Israel Damonte told Fox Sports: "We played an intelligent game. As we managed the ball well, we managed to hurt Boca.
"We knew Boca play good football but marking is a weak point, so we did not have to rush. Anyway, nothing is decided yet. We have three games remaining."
Colombian side Santa Fe went up to second in the Group 6 standings thanks to a 2-1 away win over Paraguayan side Cerro Porteno.
In Francisco Arce's debut as Cerro Porteno head coach, Jonathan Fabbro put his team ahead in the 44th minute.
However, two penalties by Argentinian playmaker Omar Perez, who scored in the 58th and 77th minutes, gave Santa Fe their first win in the group to leave them on five points, two less than Peru's Real Garcilaso. Cerro Porteno lie at the bottom after three defeats.
Atletico Mineiro consolidated their lead in Group 3 with a 2-1 home triumph over The Strongest of Bolivia.
Jo scored the opener for Mineiro in the 57th minute, after a The Strongest defender failed to cut out a Ronaldinho pass.
Former Barcelona and AC Milan playmaker Ronaldinho doubled the lead after 72 minutes from the penalty spot after Jair Torrico fouled Marcos Rocha in the box. Luis Melgar reduced the deficit in injury-time.
Atletico Mineiro have won the three games they have played so far.
In the same group, Brazilian giants Sao Paulo played out a 1-1 draw with Argentina's Arsenal at the Morumbi.
Jadson finished an Aloisio assist in injury time of the first half, while Dario Benedetto came off the bench to equalise with a penalty three minutes after the interval.
Sao Paulo striker Luis Fabiano was sent off after the end of the game following his excessive complaints to the referee.