Victor Estrella Burgos' bid to win a fourth successive Ecuador Open was ended by Gerald Melzer, while Gael Monfils reached the quarter-finals.
Burgos had reigned supreme in Quito for the past three years but his run of dominance came to a halt, upstaged by Melzer in three sets at the ATP 250 event on Thursday.
The 37-year-old Dominican sixth seed won the opening set, however, he went down 4-6 6-1 6-4 in the round of 16.
Fellow seeds Pablo Carreno Busta, Paolo Lorenzi and Ivo Karlovic also crashed out of the tournament.
Top seed Carreno Busta fell to qualifier Andrej Martin 6-4 6-2, Italian fourth seed Lorenzi lost 7-6 (7-4) 7-5 against Roberto Carballes Baena, while big-serving Croatian and seventh seed Karlovic went down to wildcard Corentin Moutet 7-5 6-7 (3-7) 7-6 (8-6).
French third seed Monfils, however, had no such troubles after he outlasted Casper Ruud 6-4 3-6 6-4.
Monfils will face Thiago Monteiro for a place in the semi-finals after the Brazilian saw off Alessandro Giannessi 7-6 (7-4) 4-6 7-5.
Albert Ramos Vinolas - the second seed - overcame Roberto Quiroz 6-3 3-6 6-3, while eighth seed Nicolas Jarry rallied to top Stefano Travaglia 4-6 7-6 (7-5) 6-3.