The Pumas stunned the rugby world with their 25-15 victory over New Zealand in their first test for more than a year last week and Ledesma has restricted himself to tweaking his bench for Saturday's match at Hunter Stadium.
Bulldozing blindside flanker Pablo Matera will again captain the side and the experienced Nicolas Sanchez retains the number 10 shirt after scoring all of Argentina's points against the All Blacks at Western Sydney Stadium.
In the replacements, Santiago Socino replaces Facundo Bosch as back-up for starting hooker Julian Montoya, while Toulon's Facundo Isa looks set to win his first cap since August 2019 after being named as back row cover instead of Tomas Lezana.
Lucio Cinti, who failed to get on the pitch to win his first cap last week, drops out of the matchday squad with Emiliano Boffelli covering for the outside backs and potentially offering a long-range kicking option.
The Tri-Nations replaced the Rugby Championship this year after world champions South Africa withdrew and Argentina's win last week blew open the race for the title.
A win for either side on Saturday will move them above New Zealand to the top of the standings.
Meanwhile the Wallabies coach Dave Rennie has recalled experienced prop Scott Sio for the test, in one of three changes to the starting side.
The 66-test Sio was omitted for the Wallabies' 24-22 win over the All Blacks in Brisbane earlier this month but comes back in as replacement for injured loosehead James Slipper.
Tighthead prop Taniela Tupou replaces the benched Allan Alaalatoa in a recalibrated front row, while the versatile Ned Hanigan starts at blindside flanker in place of the suspended Lachie Swinton.
The win over the All Blacks was Australia's first in four tests under Rennie, and he has left his backline unchanged.