Just two weeks after clinching the Apertura title with a 5-0 aggregate win over Deportes Iquique, Universidad trumped Rangers in Talca thanks to Patricio Rubio's strike just after the hour-mark.
After Universidad just missed out on an opening goal in the first half when Ramon Fernandez crashed his shot into the crossbar, Rubio struck the winner in the 61st minute on Saturday, extending an unbeaten run in the Chile Primera Division to eight games.
Universidad Catolica, who topped the Apertura standings only to be eliminated on penalties in the semi-finals by Iquique, also won their opening round match of the Clausura season; defeating Nublense 2-1 on Sunday.
Enzo Andia gave Catolica the lead in the sixth minute before Marko Biskupovic doubled the visitors' advantage just before the half-hour mark.
A penalty to Sebastian Varas dragged Nublense back into the contest five minutes into the second half but Catolica held on for the three points.
Union La Calera took top spot with a 5-1 thrashing of Cobresal on Sunday, while Palestino sit second after a 4-0 thumping of Everton.
Iquique started the new season poorly with a 1-0 loss away to O'Higgins on Friday, while Santiago Wanderers trumped Huachipato 4-2 and Colo Colo defeated Audax Italiano 2-1.
Antofagasta and Union Espanola played out the only draw of the first round with their match ending 1-1, while Universidad de Concepcion beat Cobreloa 1-0.
