Croatia: German qualifier Bjorn Phau upset second-seeded Mikhail Youzhny to reach the quarterfinals of the Zagreb Indoors on Thursday.
Phau beat the Russian 4-6, 7-5, 6-1 and will compete in his first quarterfinal since Stuttgart in 2012.
Another qualifier and a lucky loser also made the last eight.
Youzhny, the 2012 champion, was playing well until he lost his serve in the second set when he foot-faulted. Phau used the opportunity to win four games in a row and turn the match around.
"It was not the foot fault that caused me to lose the match," Youzhny said, adding he felt sick during play.
Top-seeded German Tommy Haas came back from one set down to beat countryman Benjamin Becker 4-6, 6-3, 6-3 for his first victory in 2014.
"Every time you win you appreciate the fact," Haas said. "There is still a lot of work to be done."
Third-seeded Philipp Kohlschreiber of Germany defeated Andrey Golubev of Kazakhstan 6-4, 6-2, and Ivan Dodig notched his fourth straight win against Croatian countryman Ivo Karlovic 7-6 (5), 6-3.
"It's not easy to play against a very good friend," Dodig said. "Hopefully I can now win the title."
Russian qualifier Andrey Kuznetsov beat eighth-seeded Igor Sijsling of Netherlands 6-1, 3-6, 7-6 (5), and lucky loser Daniel Evans of Britain beat Michael Berrer of Germany 1-6, 6-1, 7-6 (4).
Dudi Sela of Israel also advanced, defeating Lukas Lacko of Slovakia 6-3, 6-2.