On 18 September 2009, Karlović hit 78 aces (77 aces on 1st serve) in a Davis Cup match against Radek Štěpánek, breaking his previous record of 51 (against Daniele Bracciali in the 2005 Wimbledon Championships) and 55 (against Lleyton Hewitt in the 2009 French Open). Only once in his ATP career has he failed to hit an ace during a match, which was in the 2008 Monte Carlo Masters against Frenchman Gaël Monfils. His record of aces in a single match was broken by both John Isner and Nicolas Mahut in the longest match in tennis history at the first round of the 2010 Wimbledon Championships, where Isner hit 113 aces and Mahut hit 103.