Boca held in Venezuela on Libertadores return
Boca striker Santiago Silva looked to have broken the deadlock in the final minute at La Carolina in the city of Barinas when he rose to a right cross from substitute winger Cristian Chavez but his header agonisingly came back off the base of the near post.
Boca, who won four of their six titles between 2000 and 2007, have a tougher assignment next when they face Brazil's Fluminense at their Bombonera ground in Buenos Aires on March 7.
Uruguay's Defensor Sporting bounced back from last week's 3-0 defeat by Velez Sarsfield of Argentina with a 2-0 win over Ecuador's Deportivo Quito in their second home match in Group Seven.
Defensor were facing weaker opposition than 1994 champions Velez at their small Luis Franzini stadium in Montevideo but they made a key change bringing on the burly Maximiliano Callorda for Ignacio Risso up front.
Callorda, who troubled the Quito central defence all night, was involved in both goals, the first when he was brought down for a 22nd-minute penalty converted by midfielder Brahian Aleman.
The striker made sure of the points when he muscled his way into the box to score left-footed from the right 11 minutes from time.
Holders Santos make their bow away to Bolivia's The Strongest at high altitude at the Hernando Siles stadium in La Paz in Group One on Wednesday as they begin their quest to win South America's elite club competition for the fourth time.
Fellow Brazilian sides Flamengo and Corinthians also open their group campaigns with away matches.
Ronaldinho's Flamengo are in Buenos Aires for Wednesday's Group Two clash with Lanus, while Corinthians visit Deportivo Tachira in Group Six.