After the financial problems of Codelco, the company owner of the club, Rancagua's club relegated to the Primera B in the 1985 season, with also possibilities of be relegated to the Tercera División for another controversies related with Codelco. The next season, with the defenders Gabriel Mendoza and Atilio Marchioni as key players, the club returned to the Primera División, after an exciting final with Lota Schwager at Talca. Years later, the club hired Manuel Pellegrini as coach for face the 1992 Copa Conmebol, in which they were eliminated by Argentine side Gimnasia de La Plata in the quarter-finals, in that occasion with players like Claudio Borghi, who won the 1986 FIFA World Cup celebrated in Mexico, the talented playmaker Jaime Riveros and the striker Gustavo De Luca, one of the most prolific goalscorers in the Chilean football during the 1990s.