Third-tier outfit Deportivo Santamarina needed a late equaliser to draw 1-1 at home to Sacachispas before winning the penalty shootout 3-1.
The visitors looked in trouble after a half-hour when Adrian Pelosi was sent off for picking up a second yellow card.
But they took a shock lead five minutes before full-time through Alcides Miranda at the Estadio Municipal General San Martin de Tandil.
Roman Strada equalised for the hosts just three minutes later and they got through against the fourth-tier side in the shootout.
In another clash between third- and fourth-tier teams, Juventud Unida Universitario prevailed 4-2 on penalties against Defensores de Cambaceres after their match finished 0-0.
Dario Tempesta's men edged through as expected against their lower-tier rivals.
The teams joined Talleres de Cordoba after the second-tier outfit edged Chaco For Ever 2-1 thanks to Juan Tevez's 95th-minute winner.
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