The 10 fresh faces include: Facundo Cardozo, Franco Carrera, Agustin Fraga, Francisco Moreno, Benjamin Ordiz, Leonel Oviedo, Juan Penoucos, Juan Martin Scelzo, Mateo Soler and Tobias Wade.
Having now begun their training camp in Cardales, Los Pumas will host the Springboks at the Jose Amalfitani Stadium in Buenos Aires on 8 August, before welcoming the Wallabies to Jujuy on 29 August, and later Mendoza on 5 September.
"These three upcoming matches are very important for us," Contepomi said. "We'll be hosting the two-time world champions and playing a series against the Wallabies, which always presents very challenging encounters. The goal is to have excellent preparation and be ready for these matches.
"Physical and mental health is crucial for us, and that's why several players will be rested, allowing us to broaden the squad and work with new players. As we always emphasise, our goal is to prepare players to be successful with Los Pumas.
"I also wanted to express my gratitude for the support of the fans these past few weeks in Cordoba, San Juan, and Santiago del Estero. The next three matches will be our last in Argentina, and we are very happy to say goodbye in Velez, Jujuy, and Mendoza."
Argentina last appeared in a controversial defeat to England, in which Contepomi was criticised for his behaviour following a feisty end to the match.
This disapproval came from many angles, not least from former England scrum-half Ben Youngs, who said: "His behaviour at Twickenham [in November] was the same and you've seen players at the end of the game after the TMO and the ref has made the decision to surround the ref.
"It's totally disgraceful, unforgivable behaviour. I hope that World Rugby take it seriously, I hope there's bans dished out, no one wants to see that in our game and the fact they think that's okay is an absolute disgrace - it's awful."
Following the match, both captain Julian Montoya and fly-half Tomas Albornoz have been issued with bans, which leave them unavailable for these Tests.
Argentina 34-man squad to face South Africa and Australia
Forwards: Rodrigo Martinez, Mayco Vivas, Boris Wenger, Leonel Oviedo, Ignacio Ruiz, Pedro Delgado, Francisco Moreno, Tomas Rapetti, Franco Carrera, Efrain Elias, Tomas Lavanini, Guido Petti, Facundo Cardozo, Benjamin Grondona, Pablo Matera, Juan Penoucos, Joaquin Moro, Juan Martin Scelzo
Backs: Simon Benitez Cruz, Gonzalo Bertranou, Agustin Moyano, Geronimo Prisciantelli, Nicolas Roger, Faustino Sanchez Valarolo, Benjamin Ordiz, Lucio Cinti, Agustin Fraga, Matias Moroni, Rodrigo Isgro, Ignacio Mendy, Santiago Pernas, Santiago Carreras, Mateo Soler, Tobias Wade