HAMBURG, Germany (AP) -- Lukas Rosol upset 2006 champion Tommy Robredo of Spain 7-5, 7-6 (6) to reach the Hamburg Open quarterfinals on Thursday.
The 42nd-ranked Czech saved seven break points while converting his one chance, and took nearly two hours to put away the No. 3 seed.
Rosol, who lost in the final in Stuttgart against Roberto Bautista Agut on Sunday, awaits either Philipp Kohlschreiber or 2011 champion Gilles Simon.
German wild card Tobias Kamke knocked out the fourth-seeded Alexandr Dolgopolov 7-5, 2-6, 7-5 in just over two hours.
The 83rd-ranked Kamke next faces 17-year-old Alexander Zverev, another Hamburg native, who defeated Santiago Giraldo of Colombia 6-4, 7-6 (6) to keep his breakthrough run going.
The 285th-ranked Zverev defeated No. 5 seed Mikhail Youzhny of Russia on Wednesday.
Also winners were Argentina's Leonardo Mayer, Spain's Pablo Andujar, and Dusan Lajovic, who was leading 3-1 when fellow Serb Filip Krajinovic retired due to illness.