The 37-year-old Messi was not included in the 28-man squad following an ankle injury sustained during last month's Copa America final in the United States.
The Inter Miami player is currently recovering at his club.
River Plate goalkeeper Franco Armani was also left out of the squad, as was striker Angel Di Maria, who announced his retirement from the national team after the Copa America.
Coach Lionel Scaloni named midfielder Ezequiel Fernandez and striker Valentin Castellanos for the first time, along with young players with few international caps, including Alejandro Garnacho, Valentin Carboni, Valentin Barco and Matias Soule.
Argentina host Chile at the Monumental stadium in Buenos Aires on Sept. 5 before facing Colombia five days later in Barranquilla.
Squad:
Goalkeepers: Walter Benitez (PSV Eindhoven), Geronimo Rulli (Olympique de Marseille), Juan Musso (Atalanta), Emiliano Martinez (Aston Villa).
Defenders: Gonzalo Montiel (Sevilla), Nahuel Molina (Atletico Madrid), Cristian Romero (Tottenham Hotspur), German Pezzella (River Plate), Leonardo Balerdi (Olympique Marseille), Nicolas Otamendi (Benfica), Lisandro Martinez (Manchester United), Nicolas Tagliafico (Olympique Lyonnais), Valentin Barco (Brighton & Hove Albion).
Midfielders: Guido Rodriguez (West Ham United), Alexis Mac Allister (Liverpool), Enzo Fernandez (Chelsea), Giovani Lo Celso (Tottenham Hotspur), Ezequiel Fernandez (Al Qadsiah), Rodrigo De Paul (Atletico Madrid), Nicolas Gonzalez (Fiorentina), Leandro Paredes (AS Roma).
Forwards: Alejandro Garnacho (Manchester United), Matias Soule (AS Roma), Giuliano Simeone (Atletico Madrid), Valentin Carboni (Olympique Marseille), Julian Alvarez (Atletico Madrid), Lautaro Martinez (Inter Milan), Valentin Castellanos (Lazio).
