Jones has been withdrawn as a precautionary measure to allow him more time to recover from a calf problem which saw him withdraw from the starting line-up against England at Twickenham three weeks ago.
The Scarlets playmaker was considered ready to make a return to action but, after experiencing some further problems at the Captain’s run at the Millennium Stadium the decision was taken this morning (Saturday) to air on the side of caution and not risk the player against the Pumas.
Centre Williams, who will wear the number 21 jersey, is set to win his fourth cap, if required from the bench, after impressing coaches from the bench in outings against the Barbarians and England, twice, already this summer.
Wales v Argentina, Millennium Stadium, Saturday 20 Aug, 2011 (KO 2.30pm)
WALES:Lee Byrne; Leigh Halfpenny, Jonathan Davies, Jamie Roberts, George North; James Hook, Tavis Knoyle; Paul James, Richard Hibbard, Adam Jones, Bradley Davies, Alun Wyn Jones, Dan Lydiate, Martyn Williams (captain), Andy Powell.
Replacements: Huw Bennett, Ryan Bevington, Jonathan Thomas, Justin Tipuric, Lloyd Williams, Scott Williams, Aled Brew
Argentina 15 Martin Rodriguez, 14 Horacio Agulla, 13 Marcelo Bosch, 12 Santiago Fernandez, 11 Gonzalo Camacho, 10 Felipe Contepomi (c), 9 Nicolas Vergallo, 8 Juan Fernandez Lobbe, 7 Juan Manuel Leguizamon, 6 Julio Farias Cabello, 5 Patricio Albacete, 4 Manuel Carizza, 3 Juan Figallo, 2 Mario Ledesma, 1 Rodrigo Roncero.
Replacements: 16Agustin Creevy, 17 Martin Scelzo, 18 Mariano Galarza, 19 Alejandro Campos, 20 Agustin Figuerola, 21 Nicolas Sanchez, 22 Juan Imhoff
