Cobreloa capitalised on Universidad Catolica's loss to claim top spot in the Chile Primera Division at the weekend.
Hugo Droguett's brace saw Cobreloa past Cobresal 2-0, while Universidad were beaten for the first time this season.
O'Higgins were 2-1 winners at Universidad Catolica in a clash which saw both sides reduced to 10 men.
At the Estadio Regional Calvo y Bascunan in Antofagasta, Droguett scored once in each half for Jorge Garcia's Cobreloa.
Luis Figueroa's first-half brace had O'Higgins cruising to victory and they were in control when Enzo Andia was sent off for Universidad Catolica.
Figueroa went from hero to villain on 67 minutes when he too was red-carded, but his side held on despite substitute Alvaro Ramos' late strike.
Jorge Elizondo also scored and was sent off but his Antofagasta side were beaten 2-1 by Deportes Iquique.
Universidad Chile had few problems getting past Audax Italiano 2-0, while Universidad Concepcion left it late to edge Rangers 2-1.
Diego Chaves' penalty was enough for Palestino as they beat Colo Colo 1-0 and Matias Donoso's brace saw Santiago Wanderers past Union La Calera 3-1.
Everton lost their third league game in four in a 2-1 defeat at Union Espanola and Nublense moved off the bottom with a 3-1 win – their first of the season – over Huachipato.