Sclavi was injured in Friday’s captain’s run, and Tomas Rapetti is now in line to make his Argentina debut off the replacements' bench.
Argentina are out of the running for the Rugby Championship title but South Africa will retain the trophy with a bonus-point victory, while a win without a bonus-point would also likely make the Springboks champions again.
The match kicks off at 1300 GMT.
Updated Argentina team:
15-Santiago Carreras, 14-Bautista Delguy, 13-Justo Piccardo, 12-Santiago Chocobares, 11-Juan Cruz Mallia, 10-Geronimo Prisciantelli, 9-Simon Benitez Cruz, 8-Santiago Grondona, 7-Marcos Kremer, 6-Pablo Matera, 5-Pedro Rubiolo, 4-Guido Petti, 3-Francisco Coria Marchetti, 2-Julian Montoya (captain), 1-Mayco Vivas.
Replacements: 16-Ignacio Ruiz, 17-Boris Wenger, 18-Tomas Rapetti, 19-Franco Molina, 20-Juan Martin Gonzalez, 21-Joaquin Oviedo 22-Agustin Moyano, 23-Rodrigo Isgro.