Top seeds Nikolay Davydenko and Andy Roddick fell by the wayside in the quarter-finals of the Poertschach International on Thursday.
Defending champion Davydenko, the top seed, struggled to keep pace with Argentina's Juan Monaco and slumped to a 6-2, 6-7, 6-4 defeat.
French youngster Gael Monfils upset American world number three Roddick 7-5, 6-3 to reach the semi-finals.
Following a sluggish start, Davydenko appeared to be back in control when he clinched the second set 7-5 in a tiebreak but could not sustain the momentum.
The Russian remained confident about his prospects at the French Open, which begins on Sunday, despite the defeat.
"Mentally and physically it was draining because I had to come back from losing the first set," said Davydenko.
"I have time to prepare for Roland Garros and things should be okay."
Monaco will next face Peru's Luis Horna, a 7-6, 6-7, 6-1 winner over Albert Montanes.
Monfils, a wildcard entry at the Austrian event, will next face fourth seed Lleyton Hewitt after the Australian demolished Argentina's Diego Hartfield 6-2, 6-2.