Freddy Garcia's Real Garcilaso side moved top of Group A with a 2-1 victory at Sport Huancayo, seeing Sporting Cristal slip to second two points adrift.
The previous group leaders were beaten 4-2 by Cesar Vallejo and look set to miss out on a finals place with one game remaining.
A Fabio Ramos penalty and Mauricio Montes goal just before half-time led Real Garcilaso to their win at the Estadio Huancayo.
The hosts were reduced to 10 men on the half-hour mark when Rafael Farfan was sent off after picking up two yellow cards.
Sergio Ibarra pulled a goal back for Sport Huancayo in the first minute of additional time but the visitors held on.
Cesar Vallejo struck twice in the final 11 minutes in their surprise win over Sporting Cristal.
Daniel Chavez completed his brace in the 79th minute to put Cesar Vallejo, who had led 2-1, back ahead before Andy Pando sealed the three points.
Universitario, who have sealed top spot in Group B and their place in the 2014 Copa Libertadores second stage, drew 0-0 at home to Universidad San Martin.
Elsewhere, Melgar and Union Comercio played out a 1-1 draw and UTC Cajamarca overcame a 10-man Leon de Huanuco 1-0.
Mauro Guevgeozian struck a brace to help Alianza Lima to a 5-1 thrashing of Pacifico and Fernando Oliveira's two goals saw Inti Gas past Cienciano 3-2.
Juan Aurich netted three second-half goals to thrash Jose Galvez 4-1.
