Home favourite Ivan Ljubicic was one of three notable casualties on a hectic catch-up day at the Studena Croatia Open in Umag.
The third seed surprisingly lost his quarter-final in straight sets to Italian Potito Starace, with both men playing their second matches of the day as the tournament organisers battled to make up for the time lost when play was washed out by constant rain.
That completed a last eight laced with upsets after the top two seeds, Nikolay Davydenko and Jurgen Melzer, were also eliminated.
Davydenko and Ljubicic were expected to meet in the semi-finals, but the Russian - who had eased into the last eight on Wednesday, hammering Stephane Robert 6-1 6-2 - came unstuck against Juan Ignacio Chela.
The Argentinian had reached this stage via a more strenuous 7-6 (7-5) 6-7 (4-7) 6-1 win over Italian qualifier Simone Bolelli, but made the most of the rest day by dropping just three games in a 6-2 6-1 win in which he broke serve seven times.
The home fans would have been lifted as that result appeared to ease Ljubicic's route to the final after a 4-6 6-4 6-2 win over local wildcard Ivan Dodig in the second round.
But their happiness turned to despair as two breaks saw Starace take the opening set 6-4 and the world number 64, who had hammered Germany's Bjorn Phau 6-4 6-0 earlier in the day, saved two set points from 6/4 down in a second-set tie-break to complete a 6-4 7-6 (8-6) win.
The backlog meant Melzer was left to play three matches on one day - the third being his doubles quarter-final alongside Philipp Petzschner - and he began well with an emphatic 46-minute mauling of Jan Hajek.
Melzer broke five times and only faced two break points on his own serve as he cruised to a 6-1 6-0 success - but the Austrian stalled when later faced with the challenge of eighth seed Andreas Seppi.
The Italian had beaten Olivier Rochus of Belgium 6-4 6-2 in his opening match of the day and, with no doubles duty awaiting him, poured his resources into a 6-1 6-4 triumph against the second seed.
Top seeds Melzer and Petzschner went on to lose 6-1 6-3 to Czecho-Slovak pair Leos Friedl and Filip Polasek.
Seppi will face Juan Carlos Ferrero in the semi-finals after the Spaniard eased past Alexandr Dolgopolov of the Ukraine.
Both players were playing their only match and it proved a mere 50-minute workout, the fourth seed prevailing 6-1 6-2 after breaking twice in each set.
At the Allianz Suisse Open top seed Mikhail Youzhny crashed out to qualifier Yuri Schukin in Gstaad.
The Russian world no. 14 was expected to breeze through his quarter-final against his opponent from Kazakhstan but went down in three sets, 6-3 2-6 7-5.
Richard Gasquet continued his progress in Gstaad with a quarter-final victory against Albert Montanes.
The French seventh seed was in impressive form to oust his fourth-seeded opponent 7-6 (7/5) 6-4 and progress to the semi-final stage.
In other action, Nicolas Almagro of Spain was a 6-2 7-6 (7-5) winner against Jeremy Chardy while Daniel Gimeno-Traver beat Igor Andreev 6-2 6-4.