The struggles of Boca Juniors continued as they slumped to a 1-0 home defeat against Nacional in the Copa Libertadores on Thursday.
Boca Juniors have won the tournament six times – only fellow Argentine side Independiente have won it more – while they have finished runner-up on four occasions.
Uruguayan side Nacional have also enjoyed plenty of success in the competition, winning three finals and losing another three, making this match a true clash of South American titans.
Boca made the Copa Libertadores final last year before being defeated by Corinthians of Brazil, but they have not made such a good start to this season.
They have won just one of their four league games in the Argentine top-flight, leaving them 15th on the table, and they conceded early against Nacional.
Andre Scotti scored the goal, converting Juan Albin's assist after 20 minutes.
And Boca were unable to score an equaliser despite having a numerical advantage for the latter stages of the game.
Nacional defender Alejandro Lembo was sent off for a second yellow card with 16 minutes to play but the visitors held firm to claim a crucial Group 1 win.
The Uruguayan side have now claimed seven points from their three group stage fixtures, which sees them on top, while second-placed Toluca of Mexico (four points) remain ahead of the third-placed Boca (three points).
Brazilian side Atletico Mineiro made it three wins from as many matches in Group 3 with a 2-1 success against The Strongest of Bolivia.
After a goalless first half, former Manchester City striker Jo opened the scoring after 57 minutes.
And attacking star Ronaldinho doubled the advantage with 17 minutes to play, meaning Luis Melgar's late goal was merely a consolation for the losers.
In the same group, Brazil's Sao Paulo were held to a 1-1 home draw against Arsenal of Argentina while in Group 6, a pair of second-half penalties to Omar Perez helped Colombian side Santa Fe win 2-1 at Paraguayan club Cerro Porteno.