Karlovic upsets Berdych in opening round of Qatar Open
Karlovic served 25 aces and had 49 winnersh, while Berdych had eight aces and 28 winners. Neither player managed to break serve.
Berdych was the only top 10 player who did not win an ATP tour title in 2013.
Karlovic, a former top 15 player, finished the 2013 season ranked No. 77. He missed nearly two months in the spring when he became ill with spinal meningitis.