Top seed Ivo Karlovic went down to defending champion Victor Estrella Burgos in the Ecuador Open second round.
Karlovic served 39 aces, but was edged 6-7 (7-9) 7-6 (7-5) 7-6 (10-8) in a thrilling clash on the clay in Quito on Thursday.
The Croatian had three match points in the third set but failed to capitalise before losing in two hours, 11 minutes.
Neither player managed to create a break point throughout the contest, with only 10 points won against serve in the deciding set.
Estrella Burgos, winner of the event in 2015 and 2016, next faces Federico Gaio after the Italian qualifier continued his run with a 6-7 (4-7) 6-3 7-6 (7-2) win over Gerald Melzer.
Italian third seed Paolo Lorenzi booked his spot in the last eight in far more comfortable fashion, easing past Australian Matthew Ebden 6-4 6-4.
Awaiting Lorenzi in the quarter-finals is Rajeev Ram after the American overcame Nicolas Kicker 7-6 (7-5) 6-3.
Only four of the eight seeds reached the quarter-finals at the ATP 250 event.