of his career in five sets. In the second round, he met Stanislas Wawrinka, to whom he lost in straight sets. 2014: Four ATP finals and return to top 30 In February, Karlović reached the final of the U.S. National Indoor Tennis Championships, losing to Kei Nishikori. In May, he reached the final of the Düsseldorf Open, losing to Philipp Kohlschreiber. In July, he reached the final of the Hall of Fame Open, losing an epic match to Lleyton Hewitt. Another solid week of tennis saw him make back-to-back finals, this time at the Claro Open Colombia, losing to Bernard Tomic in a tight three-setter. He avenged that loss the following month at the Rogers Cup in another tight three-setter. 2015: Sixth ATP title and return to top 20 Karlović won his sixth title, defeating Donald Young at the Delray Beach Open. He also won the 2015 Topshelf Open in doubles with Łukasz Kubot. He reached his second Hall of Fame Open final, which he lost to Rajeev Ram in three sets. 2016: Seventh & eight titles as oldest champion since 1979, return to top 20 Karlović suffered a knee injury and missed two months of play. He reached the final of the Hall of Fame Open for the third time against Gilles Müller, which he won in three tiebreaks. At the age of 37 and 5 months, he became the oldest player to win an ATP title since 1979. He reached an ATP World Tour 500 series tournament at the Washington Open (tennis), which he lost to Gaël Monfils. He then won the Los Cabos Open, beating Feliciano López in straight sets and returned to the top 20 again at 37 years and 6 months. 2017: 75 Aces at Australian Open Karlović began the Australian Open by defeating Horacio Zeballos in a 5-hour, 15-minute match, the second-longest match at the tournament in the Open Era (behind the Djokovic–Nadal final in 2012). He set an Australian Open record, hitting 75 aces. Aged 38, Karlović set up the oldest ATP Tour tournament final in 41 years against Gilles Muller, aged 34, at the 2017 Ricoh Open. He lost in straight sets. 2018: Defying age At the Australian Open, Karlović progressed to the Round of 32, losing to Andreas Seppi, 7–9 in the fifth set. At the Ecuador Open in Quito, Karlović made it to the Round of 16, losing to 18