Croatia's Ivo Karlovic will take on Jiri Vesely of the Czec Republic in the Duesseldorf Open semifinals.
Croatia's Ivo Karlovic will take on Jiri Vesely of the Czec Republic in the Duesseldorf Open semifinals.
CAROLINE SEIDEL/EPA

DUESSELDORF, Germany (AP) - Ivo Karlovic of Croatia advanced to the Duesseldorf Open semifinals on Thursday, hitting 19 aces in a 6-4, 3-6, 6-3 win over defending champion Juan Monaco of Argentina.

The seventh-seeded Karlovic will meet Jiri Vesely of the Czech Republic on Friday. Vesely spoiled Jurgen Melzer's 33rd birthday by beating the Austrian 6-1, 6-1 to advance to his first ATP semifinal.

Melzer is playing again after missing seven months with a shoulder injury.

Denis Istomin of Russia upset third-seeded Andreas Seppi of Italy 6-3, 6-4 to record his 150th career win.

The match between top-seeded Philipp Kohlschreiber of Germany and qualifier Mate Delic of Croatia was interrupted twice by rain and finally abandoned because of darkness, with Kohlschreiber leading 7-5, 4-4. Delic is in his first tour-level event.

Copyright 2014 Associated Press. All rights reserved. This material may not be published, broadcast, rewritten, or redistributed.

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