Argentina lock Pedro Rubiolo will miss Saturday's Rugby Championship clash against Australia in Santa Fe.
Rubilio must follow concussion protocols after being forced from the field early in last Saturday's 20-19 loss to the Wallabies in La Plata.
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The lock suffered a blow to the head in the opening minutes of the Test and had to leave the field for a head-impact assessment (HIA), which he failed.
As a result, he sits out the return clash between the two countries in the southern hemisphere championship but will remain with the team, the Argentine Rugby Union said on Monday.
Replacement scrum-half Lautaro Bazan Velez suffered a muscle strain in the warm-up before the match in La Plata and is out, along with loose forward Bautista Pedemonte, who is injured but did not compete in last Saturday's Test.
Veteran former captain Agustin Creevy has also left the camp after his last international, celebrating his 110th cap in front of his home crowd with a cameo appearance on Saturday.
Uncapped hooker Bautista Bernasconi replaces Creevy in the squad, while Tomas Cubelli comes in for Bazan Velez.
The 32-year-old lock Matias Alemanno, who made his debut for the Pumas 11 years ago, returns to the squad as a back-up for Rubiolo, the Argentine union said.
Australia kicked over a last-gasp penalty to edge Argentina in last Saturday's clash, leaving both teams with two defeats from three matches in this year's Rugby Championship.
This Saturday's clash at Santa Fe's Estadio Brigadier General Estanislao Lopez is Argentina's first Test in the city since losing 30-12 to Wales in 2018.