Swede Robin Soderling needed 20 aces and two tiebreaks to down top seed Andy Roddick 7-6, 7-6 and reach the semi-finals of the Lyon ATP tournament on Friday.
Soderling, seeded seventh in the indoor event, won both tiebreaks 7-5 to take a tight contest in an hour and 23 minutes.
Both players held serve throughout a match in which Roddick fired 22 aces but showed signs of nerves at times, notably when he double-faulted in the second set tiebreak.
Soderling, who won the tournament in 2004, now leads American Roddick 2-0 in career meetings after beating the former world number one in February in Memphis.
"I love it here and I feel capable of winning it again because I'm playing really well at the moment," warned the Swede, ranked 27th in the world.
Soderling goes on to meet Gilles Simon, who beat wildcard Josselin Ouanna 6-3, 7-5 in an all-French quarter-final match.
Fourth seed Simon, playing his first tournament as a Top 10 player after beating world number one Rafael Nadal on his way to the Madrid final last week, showed more composure when it mattered.
Roddick, sixth in the ATP Race standings, did his chances of making next month's season-ending Masters Cup featuring the world's top eight players in Shanghai no favours with the defeat.
"He played better than me in the rallies but this was a good preparation for Bercy," said Roddick, looking forward to the Paris Masters Series tournament starting on Sunday.
"It's a long season," Roddick added. "Whoever tells you he's not tired is lying."
Simon, who was ninth in the ATP Race at the start of the week, still has a chance of earning a Masters Cup slot.