Boca Juniors were held to a 0-0 draw by Venezuelan hosts Zamora on Tuesday in the Argentine power club's opening match in the group stage of this season's Copa Libertadores.
Zamora was playing its first ever game in the continental competition, while Boca Juniors has won the competition on six occasions and is among the favorites this year.
In other games Tuesday, Colombia's Atletico Nacional had a 2-0 home win over Universidad de Chile 2-0, and Uruguay's Defensor Sporting also won 2-0 at home against Deportivo Quito of Ecuador.
In Group 4, Boca Juniors, which won the Argentine Apertura championship going undefeated in 19 games and conceding just six goals, did not create many clear cut chances against Zamora, despite enjoying the majority of possession.
Uruguayan Santiago Silva came closest for Boca Juniors with a header that hit the post and rebounded into the goalkeeper's arms in the 90th minute.
Silva was making his debut for Boca Juniors after signing from Italian team Fiorentina in January. He is only eligible to play in the Copa Libertadores, not the domestic league.
"We couldn't get the three points we wanted, but a point helps us," Zamora's Jaime Bustamente said after the game.
The Group 4 opener was last week, when Brazil's Fluminese won 1-0 at home against Argentine side Arsenal.
In Medellin, Colombia, Atletico Nacional's Juan Valencia opened the scoring with a left foot volley from inside the penalty area in the 29th in the Group 8 game.