Andrés Gallegos ruined the script by beating Castle's Alex Gleeson in the last 16 and now faces Whitehead's John Ross Galbraith in Saturday morning's quarter-finals of the Argentinian Amateur Championship in Buenos Aires.
After seeing off leading qualifier Kyle McLatchie of South Africa in round one, Gleeson defeated Colombia's Johan Sebastian Lopez Bulla 2 and 1 in Friday morning's second round but fell 2 down to world 665 Gallegos in the afternoon.
Had he won, the Irish Close champion would have squared off with Galbraith in the last eight after the Whitehead player beat Axel Ochoa 3 and 2 and then Nicolás Moyano by 4 and 3 after lunch.
Four Argentinians and four overseas players will contest the quarter-finals with Galbraith taking on the winner of the Argentinian Order of Merit in Gallegos.
Andy Schonbaum will face Chile's Cristóbal del Solar, who was second in the Copa Tailhade and yesterday beat the winner of that event, Augustin Tarigo, in the last 16.
Juan Cruz Rocca beat Spain's Adriá Arnaus and will face fellow Herik Machado de Oliveira of Brazil while Mauro Báez Julién beat Uruguayan Julián Fedele.
Julién now takes on another Uruguyam in Juan Álvarez, who is 27th in the World Amateur Golf Ranking and finished second ahead of the likes of Angel Cabrera in last year's VISA Open de Argentina.
The semi-finals will take place on Saturday afternoon with the 36-hole final set for Sunday.
Argentinian Amateur Championship, Estancias Golf Club, Buenos Aires
- GALLEGOS ANDRES GERMAN v GALBRAITH JOHN ROSS (IRL)
- MACHADO OLIVEIRA, HERIK (BRA) v ROCCA JUAN CRUZ
- SHONBAUM ANDRES (H) v DEL SOLAR CRISTOBAL (CHI)
- ALVAREZ JUAN (URU) v BAEZ JULIEN MAURO ANTONIO