The former Valencia and Roma midfielder, his Velez Sarsfield team-mate Gino Peruzzi and Boca Juniors goalkeeper Agustin Orion were named on the Argentine FA website.
Playmaker Gago is a key member of coach Alejandro Sabella's squad, leaders in the South American group, who face Colombia at home on Friday and visit Ecuador four days later.
Argentina top the group with 24 points from 11 matches. Ecuador have 20 points and Colombia 19, both with a match in hand.
The top four teams at the end of the qualifiers in October will go through to the Brazil finals. The fifth-placed team, at present Venezuela, will enter a playoff against an Asian qualifier in November for another berth.
Revised squad:
Goalkeepers: Sergio Romero (Sampdoria), Mariano Andujar (Catania), Agustin Orion (Boca Juniors).
Defenders: Pablo Zabaleta (Manchester City), Hugo Campagnaro (Napoli), Ezequiel Garay (Benfica), Federico Fernandez (Getafe), Fabricio Coloccini (Newcastle United), Jose Basanta (Monterrey), Marcos Rojo (Sporting Lisbon), Gino Peruzzi (Velez Sarsfield).
Midfielders: Javier Mascherano (Barcelona), Fernando Gago (Velez Sarsfield), Ever Banega (Valencia), Walter Montillo (Santos), Jose Sosa (Metalist Kharkiv), Augusto Fernandez, (Celta Vigo), Lucas Biglia (Anderlecht), Pablo Guinazu (Libertad), Angel di Maria (Real Madrid), Erik Lamela (AS Roma).
Forwards: Lionel Messi (Barcelona), Gonzalo Higuain (Real Madrid), Ezequiel Lavezzi (Paris Saint-Germain), Rodrigo Palacio (Inter Milan), Sergio Aguero (Manchester City).
