The league leaders scored twice in the first half through Michael Rios and Cristian Alvarez to remain three points clear of O'Higgins, who won 1-0 against Cobreloa.
Pedro Hernandez scored O'Higgins' winner in the 80th minute.
Union Espanola extended their unbeaten run to five games after a 1-0 home triumph over Union La Calera.
The only goal of the game came from Lorenzo Faravelli on 68 minutes with Espanola moving to sixth place - only short of the final series' positions by goal difference.
Rangers pulled off a shock as they won 3-0 at 10-man Santiago Wanderers.
First-half goals to Mauricio Gomez and Esteban Ciacchieri established a two-goal lead before the former struck again early in the second period.
Wanderers' day was furthered soured by the sending off of Boris Sagredo in the 78th minute.
In other matches, Palestino defeated Cobresal 2-1, Colo Colo snuck a 3-2 win against Universidad Chile and there was a goalless draw between Huachipato and Universidad Concepcion.
Deportes Iquique triumphed 2-1 over Audax Italiano and Nublense won 2-1 at home against Antofagasta.
