Camilo Mayada equalised with three minutes remaining as visiting River rescued a 2-2 draw against Flamengo in Rio de Janeiro on Thursday (AEDT).
Argentinean giant River twice trailed and responded on both occasions in the four-goal Group Four thriller at Estadio Nilton Santos.
After a scoreless opening half, Henrique Dourado converted a 54th-minute penalty to put Brazilian host Flamengo ahead.
Flamengo's lead lasted barely a minute as Rodrigo Mora glanced a header past former Valencia goalkeeper Diego Alves.
The home side was back ahead in the 66th-minute when Everton finished powerfully beyond Franco Armani but River was not done, Mayada scoring from distance during the closing stages.
It was not the only draw midweek, with the three other fixtures ending all-square.
Roberto Ordonez cancelled out Marcos Riquelme's opener as Delfin drew 1-1 at home to Bolivar in Group Two.
Nacional played out a goalless draw with Estudiantes in Group Six, while the Group Seven clash between Millonarios and Corinthians ended 0-0.