Gael Monfils suffered a shock loss in the Ecuador Open quarter-finals as Albert Ramos-Vinolas was left as the only seed standing on Saturday (AEDT).

Monfils, the No.3 seed at the clay-court tournament in Quito, was downed by Brazilian Thiago Monteiro 6-4 2-6 6-4 in the last eight.

The Frenchman was a hot favourite to win the ATP 250 event, but Monteiro dominated the third set to progress in a surprise victory.

Monteiro will face Ramos-Vinolas in the semi-finals after the No.2 seed, from Spain, proved too good for Gerald Melzer 6-2 6-4.

Melzer upset Victor Estrella Burgos, the three-time defending champion and only player to win the tournament, in the second round.

However, he was no match for Ramos-Vinolas, who faced just one break point in a convincing display.

Ramos-Vinolas is the only seed remaining after Nicolas Jarry was edged out by Roberto Carballes Baena 3-6 6-2 7-6 (7-5).

Carballes Baena will face fellow qualifier Andrej Martin in the last four after the Slovakian beat teenage wildcard Corentin Moutet 6-3 6-4.