Boca Juniors played out a goalless draw with Zamora in their Copa Libertadores Group Four clash, leaving both sides on a point.
Boca striker Santiago Silva appeared to have claimed a last-gasp winner at La Carolina when he nodded a Cristian Chavez cross, only to see his header cannon back off the near post.
Zamora were the happier of the sides and defender Jaime Bustamante said: "This point is good as we are starting the dream of qualifying to the next round. We thought Boca were going to be tough. We tried to play them as good as possible. We are happy for our defensive job."
His coach, Julio Falcioni, endorsed his defensive work, adding: "They did not let Boca play. We thought they were going to play better football, but they did their job. They got what they wanted - a 0-0 draw."
Defensor Sporting put their opening Copa Libertadores loss to Velez Sarsfield behind them by beating Deportivo Quito 2-0 in Group Seven.
A 22nd-minute penalty from Brahian Aleman put them ahead, with Maximiliano Callorda doubling their lead 12 from the end.
"It was a must-win game for us,'' Callorda said. "We did our best on the field. We were not the worst team after we lost to Velez and we are not the best now that we beat Deportivo Quito. We must keep fighting.''
Atletico Nacional also got off to a winning start in Group Eight as they beat Universidad de Chile 2-0.
Juan Valencia opened the scoring in the 28th minute and Dorlan Pabon wrapped things up with 10 minutes left.