Born in Zárate, Buenos Aires, Ahumada made his professional debut with Club Atlético River Plate on 24 November 2002, in a 2–1 victory against Olimpo de Bahía Blanca.

He played a small part in helping River to the Clausura 2003 and 2004 championships before moving to Germany in 2004 for a short spell with VfL Wolfsburg, where he joined compatriots Facundo Quiroga, Andrés D'Alessandro, Juan Carlos Menseguez and Diego Klimowicz.

This altercation began after the elimination at the hands of fellow league side San Lorenzo de Almagro in the 2008 Libertadores Cup round of 16.

During the whole crisis after the Libertadores elimination, River Plate still had strong chances of winning the Clausura, and battled head-to-head with Estudiantes de La Plata and eventually won, with Ahumada playing a key role along with Ariel Ortega, Juan Pablo Carrizo and young prospect Diego Buonanotte.

Ahumada was part of the Argentina squad that won the 2001 FIFA World Youth Championship on home soil.