Karlovic equals aces record
Ivo Karlovic equalled the record for aces in a three-set match with 44 in a tense clash with Daniel Brands in Zagreb.
The towering Croat beat Brands 6-7 7-5 7-6 to progress to the second round of the indoor tournament in his homeland.
He constantly beat the German with his precise serves and by the end of the match had done enough to match the ATP Tour record set by Australia's Mark Philippoussis.
Philippoussis delivered 44 aces against Zimbabwe's Byron Black in a 1995 match in Kuala Lumpur, Malaysia - Gary Muller once hit 54 but that was in a three-set qualifying match for Wimbledon.
There was also a win on Tuesday for Michael Berrer of Germany who defeated home hope Borna Coric 6-4 3-6 6-4.
Germany's Bjorn Phau defeated another Croatian player Ante Pavic 6-3 6-4, Dusan Lajovic beat fellow Serb Pedja Krstin 6-2 6-3 and Lukas Lacko of Slovakia defeated German Jan-Lennard Struff 6-4 6-4.