Marin Cilic won a battle of big servers, with a key service breaking helping him beat American John Isner 7-5, 3-6, 7-6 (6), 6-4 to advance to the U.S. Open's round of 16.
Cilic, the No. 22 seed and 2014 champion at Flushing Meadows, earned the crucial break in the fourth set to get the advantage. The 14th-seeded Isner fought back a pair of match points before Cilic finally put it away on his serve to advance to a Grand Slam tournament fourth round for a 23rd time.
Isner finished the day with 40 aces and only four double faults. Cilic had 21 aces but 17 double faults. Both players converted on about 80 percent of their first-serve points, but Cilic saved 13 of 14 break point chances.
Next up for Cilic is No. 2 Rafael Nadal, who beat Hyeon Chung in straight sets.
Earlier on Louis Armstrong Stadium, No. 6-seeded Alexander Zverev beat Aljaz Bedene 6-7 (4), 7-6 (4), 6-3, 7-6 (3).
