Argentina will be without skipper Felipe Contepomi for their crucial World Cup Pool B clash with Romania on Saturday.
The fly-half, 34, was left with badly bruised ribs following the narrow 13-9 loss to England in their opener.
The Pumas will also be without centre Gonzalo Tiesi for the rest of the tournament due to a leg injury.
Romania coach Romeo Gontineac has retained the same pack but made three changes in the backline.
Argentina led for much of their match against England but they finished the game defeated and with a raft of injuries.
Coach Santiago Phelan has drafted in Santiago Fernandez to replace Contepomi, with number eight Juan Martin Fernandez Lobbe taking the captaincy.
Marcelo Bosch comes in for former London Irish and Harlequins outside centre Tiesi, who suffered ligament damage to his right knee. Lucas Gonzalez Amorosino moves to full-back, with Martin Rodriguez switching to centre. Fernandez plays at fly-half.
On a positive note, veteran hooker Mario Ledesma, 38, is back to full fitness and will set a new record when he plays in his 15th World Cup match for Argentina.
He previously shared the record of 14 with Agustin Pichot and Contepomi.
Romania, who delivered a powerful pack display against Scotland before running out of steam in the last 10 minutes and losing by 10 points, have made three changes.
Tiberius Dimofte moves from centre to start at fly-half as Marin Dumbrava drops to the bench and will partner Florin Surugiu, who was preferred at scrum-half to veteran Lucian Sirbu.
Centre Constantin Gheara and wing Ionel Cazan were also named in the starting line-up.
Argentina: Lucas González Amorosino, Gonzalo Camacho, Marcelo Bosch, Martin Rodríguez, Horacio Agulla, Santiago Fernández, Nicolás Vergallo; Rodrigo Roncero, Mario Ledesma, Juan Figallo, Manuel Carizza, Patricio Albacete, Julio Farías Cabello, Juan Manuel Leguizamón, Juan Martín Fernández Lobbe (captain). Replacements: Agustín Creevy, Martín Scelzo, Mariano Galarza, Alejandro Campos, Alfredo Lalanne, Nicolás Sánchez, Juan José Imhoff.
Romania: Iulian Dumitras, Madalin Lemnaru, Csaba Gal, Constantin Gheara, Ionel Cazan, Tiberius Dimofte, Florin Surugiu; Mihaita Lazar, Marius Tincu (captain), Paulica Ion, Valentin Ursache, Cristian Petre, Mihai Macovei, Ovidiu Tonita, Daniel Carpo. Replacements: Bogdan Suman, Silviu Florea, Valentin Poparlan, Daniel Ianus, Valentin Calafeteanu, Marin Dumbrava, Florin Vlaicu.