It's been some journey for the one-time flanker who switched to the front row and is ending his career at his fourth World Cup.
For some time he had to wait his chance as Federico Mendez wound down his illustrious career. Then he bounced into his work.
Had Argentina been a more favoured opposition, Ledesma would have strolled on to the list of those who have played 100 tests for their country.
"He has been a hell of a player for us and has never taken anything for granted in his career," a spokesman said.
"Mario never leaves anything in the tank. He deserves a standing ovation."
This tournament, Ledesma has been his usual hard-charging self, delivering his set piece work and busying himself around the field with more venom than many men half his age.
He survived a thunderous knee to the head from England lock Courtney Lawes, picked himself up from the Dunedin Stadium touchline and resumed his combat. He is one tough gaucho.
So are his mates but without injured No 8 Juan Martin Fernandez Lobbe, few give the Pumas much chance of an upset against the All Blacks on Sunday.
The quarter-final would be a battle of styles. Argentina would try to slow the game down as much as possible, walking to lineouts and working the pick'n'go plays for as long as possible.
They would search for territory and penalty concessions to give captain Felipe Contepomi opportunities to keep his side in the test.
It would not be exciting but it would be customary rugby.
The Pumas and All Blacks will announce their sides today for the test which will be refereed by Nigel Owens.