Sanz and Nieto eliminated three-seed 'Momo' Gonzalez and 'Sanyo' Gutierrez in three sets in the round of 16 at the Steffl Arena, handing Gutierrez and Gonzalez their first early exit together.
The only tournament Sanz and Nieto had played prior to this week was the Torrent Challenger last season, where they would go on to lift the title.
Elsewhere, number ones Arturo Coello and Agustin Tapia kept up their winning streak as they faced Lucas Bergamini and Victor Ruiz, while Martin Di Nenno and Franco Stupaczuk took on Jorge Ruiz and Toni Bueno.
Watch Thursday's centre-court highlights below!
Matches in chronological order:
Sanyo Gutierrez (ARG) / Momo Gonzalez (ESP) (3) vs Jon Sanz (ESP) / Coki Nieto (ESP)
Arturo Coello (ESP) / Agustin Tapia (ARG) (1) vs Lucas Bergamini (BRA) / Victor Ruiz (ESP)
Martin Di Nenno (ARG) / Franco Stupaczuk (ARG) (2) vs Toni Bueno (ESP) / Jorge Ruiz (ESP)
