Defending champion Guillermo Garcia-Lopez saved a match point before reaching the semi-finals of the Nastase Tiriac Trophy at the expense of Guido Pella.
Fourth seed Garcia-Lopez battled back from the brink of defeat to win 7-6 (7-5) 3-6 7-6 (8-6) on the clay in Bucharest on Friday.
The Spaniard lost his only previous encounter with Pella two years ago and made hard work of getting revenge to stay on course to defend his title.
Garcia-Lopez grasped only one of his break-point opportunities and went through despite failing to hold on three occasions against the Argentine.
Pella was just a point away from dumping Garcia-Lopez out at the quarter-final stage in the 10th game of the third set, but the defending champion stood firm and prevailed in a second tie-break.
Garcia-Lopez will now face Fernando Verdasco in an all-Spanish semi-final after his compatriot beat Robin Haase 7-6 (8-6) 6-3.
Haase beat top seed Bernard Tomic to book his place in the last eight, but came unstuck in a hard-fought match against Verdasco.
Lucas Poullie followed up his success against second seed Ivo Karlovic by ousting Paolo Lorenzi 4-6 6-4 7-5.
The unseeded Frenchman will now take on Federico Delbonis, who saw off Marco Cecchinato 6-2 6-2.