Japan's Kei Nishikori fended off Bradley Klahn 6-2, 4-6, 6-3, 7-5 in the US Open second round on Wednesday as the 2014 Flushing Meadows runner-up continued his bid for a first Grand Slam title. What appeared at the outset to be a routine match for the seventh-seeded Japanese turned into a surprise challenge from American Klahn. After a tepid start, Klahn won all his first-serve points in the second set and saved three of the four break point opportunities against him. Nishikori, who reached the semi-finals last year and in 2016, broke Klahn to take the third set, switching the momentum back in his favour and dominating the longer rallies. Inconsistency ultimately proved Klahn's downfall as the 29-year-old committed 62 unforced errors in the match, 30 more than his opponent. Nishikori, who had rued his lack of playing time after his first-round opponent was forced to retire, was joined by his usual crowd of excitable fans, shielded from the soggy conditions under Louis Armstrong's retractable roof. He will face either 31st-seeded Cristian Garin of Chile or Australia's Alex de Minaur in the third round.