Mercado was called up alongside five other home-based players, Boca Juniors keeper Agustin Orion, Velez Sarsfield defender Sebastian Dominguez, Newell's Old Boys and former Liverpool forward Maxi Rodriguez and midfielders Leandro Somoza (Lanus) and Rodrigo Brana (Quilmes)
"This is the reward for my effort. I'm happy and I'm in good form at the moment," Mercado said.
Argentina are the only team from the South American qualifiers to have already booked a berth at the 2014 World Cup finals with two rounds to go.
Argentina squad: Sergio Romero (Sampdoria), Mariano Andujar (Catania), Agustin Orion (Boca Juniors); Federico Fernandez (Napoli), Hugo Campagnaro (Inter Milan), Jose-Maria Basanta (Monterrey), Marcos Rojo (Sporting Lisbon), Pablo Zabaleta (Manchester City), Fabricio Coloccini (Newcastle), Ezequiel Garay (Benfica), Cristian Ansaldi (Rubin Kazan), Sebastian Dominguez (Velez Sarsfield), Gabriel Mercado (River Plate); Angel Di Maria (Real Madrid), Lucas Biglia (Lazio), Ever Banega (Valencia), Jose-Ernesto Sosa (Metalist), Augusto Fernandez (Celta), Ricardo Alvarez (Inter Milan), Erik Lamela (Tottenham), Leandro Somoza (Lanus), Rodrigo Brana (Quilmes); Mauro Icardi (Inter Milan), Ezequiel Lavezzi (Paris St Germain), Sergio Aguero (Manchester City), Rodrigo Palacio (Inter Milan), Maximiliano Rodriguez (Newell's Old Boys).