BUENOS AIRES, Jan 29 (Reuters) - Argentine champions Boca Juniors suffered a surprise 2-1 defeat by Gimnasia-Jujuy on Sunday as the Clausura title race got under way.
Gimnasia's disciplined game was enough to undo a Boca team who struggled to find any rhythm after the close-season break.
Gimnasia, tipped for relegation, carved out three clear scoring opportunities in the first half and midfielder Israel Damonte hit the post.
Boca survived these scares, however, and Martin Palermo broke the deadlock by rising to meet a cross from Juan Krupoviesa on the stroke of halftime.
Gimnasia's Damote equalised on 57 minutes after latching on to a loose ball following a shot by Gustavo Balvorin.
Boca Juniors felt the absence of injured midfielders Sebastian Battaglia and Fernando Gago, who were replaced by Pablo Ledesma and Fabian Vargas.
Hector Silva scored the Gimnasia winner from a corner on 65 minutes.
River Plate had no such problems against lowly opposition, trouncing Tiro Federal 5-0.
Daniel Montenegro bagged two goals, and Jairo Patino, Jonathan Santana, Luciano Figueroa and Ernesto Farias scored one apiece.
River Plate are hitting a rich vein of form under new coach Daniel Passarella following their 6-0 drubbing of Bolivia's Oriente Petroleo.
Banfield produced another upset by beating Racing 3-0.
Midfielder Jesus Datolo scored a goal in each half and Cristian Leiva added a third on 71 minutes.
Dario Scocco managed his own brace of goals to help Newell's Old Boys to a solid 2-0 win over Quilmes.
Independiente, another team with hopes of lifting the Clausura trophy, could only draw 0-0 at home to Lanus.
Independiente rely heavily on the talents of young striker Sergio Aguero, who is also looking to impress Argentine coach Nestor Pekerman enough to make the squad for this year's World Cup.
Played as a lone striker up against the massed Lanus defence, however, Aguero made little impression.