The Italian sealed a 6-3 1-6 6-2 victory over his Argentinian opponent in their second-round clash to set up a quarter-final meeting with Colombia’s Santiago Giraldo.
Clinical Fognini took six of the eight break points he carved out and saved nine of the 14 he faced.
Giraldo, the sixth seed, was also taken to three sets, battling back to see off another Argentinian, Carlos Berlocq, 4-6 7-5 6-3.
Elsewhere, Luca Vanni beat fellow qualifier Thiemo de Bakker from Holland 7-6 (7/5) 3-6 6-3.
The Italian will face Dusan Lajovic for a place in the semi-finals after the Serbian knocked out Fernando Verdasco 6-7 (6/8) 6-3 6-4.
Another come-from-behind winner was home hope Joao Souza, the wildcard seeing off Slovakia’s Martin Klizan 3-6 6-3 6-2 to set up a quarter-final against fourth seed Leonardo Mayer.