NEW YORK -- Marin Cilic, the US Open defending champion, looked down and out against Mikhail Kukushkin, but he scrambled to win his third-round match Friday while Novak Djokovic is through to the fourth round with another straight-sets victory.
Kukushkin was serving for the second set before Cilic found the form that helped him collect his first Grand Slam singles title a year ago. The No. 9 seed won 6-7 (5), 7-6 (1), 6-3, 6-7 (3), 6-1.
The last stroke was a 132 mph ace that elicited a celebratory swinging uppercut from Cilic.
The grinding match, played in Louis Armstrong Stadium, ran 4 hours, 11 minutes. It was the longest match of the tournament -- by 17 minutes -- so far.
A nine-time major champion, Djokovic beat 25th-seeded Andreas Seppi 6-3, 7-5, 7-5 on Friday. Djokovic had his serve broken for the first time this tournament -- Seppi did it twice -- but otherwise had little trouble improving to 11-0 against the 31-year-old Italian.
Djokovic will play No. 23 Roberto Bautista Agut of Spain, whose opponent Friday, No. 14 David Goffin of Belgium, became the 13th man to stop playing a match because of injury or illness at this major. He gave way to Bautista Agut early in the fourth set while up two sets to one.
Cilic had won 16 consecutive sets here before a botched drop shot gave Kukushkin the first frame.
The No. 56 seed from Kazakhstan knocked off Grigor Dimitrov in the second round. Kukushkin had lost in the first or second round of 16 consecutive tournaments before beating Dimitrov.
Benoit Paire continued his upset march by taking down Spain's Tommy Robredo, the 26th seed, 7-6 (6-3), 6-1, 6-1. Paire, the unseeded 26-year-old Frenchman, sunk 2014 US Open runner-up Kei Nishikori in the first round. He will meet 19th seed Jo-Wilfried Tsonga in the fourth round.
The Associated Press contributed to this report.