By Steve Keating
NEW YORK (Reuters) - Top seed Novak Djokovic and defending champion Marin Cilic took different routes into the fourth round of the U.S. Open as the upsets and searing heat at Flushing Meadows both eased off on Friday.
After a week of punishing heat that saw a record 13 players retire, cooler temperatures and order returned to the year's final grand slam as world number one Djokovic eased to a third round 6-3 7-5 7-5 victory over Italian Andreas Seppi.
Cilic also kept his title defense on track but not without a scare as the ninth seed needed over four hours to put away Kazakhstan's 56th-ranked Mikhail Kukushkin 6-7(5) 7-6(1) 6-3 6-7(3) 6-1.
The big-hitting Croat stepped onto the Grandstand court having won 16 straight sets at the National Tennis Center but that string quickly came to an end when Kukushkin took the opening set in a tiebreak in what was the start of a long and harrowing afternoon for the defending champion.
"I'm happy with the fighting spirit today, just accepting that I wasn't playing so well," said Cilic. "For sure (being defending champion) always has some weight to it.
"Playing on a big court with a full house, that's going to give you some extra motivation in the situations like today when I was a set and 5-2 down.
"I was in the thought process that I am going to stay on the court as much as necessary."
It had been a trouble-free visit to New York for Djokovic, the lanky Serb not dropping a set while losing just 10 games going into his match against Seppi.
But the 25th-ranked Italian at least made Djokovic work for his spot in the round of 16, the world number one needing a tiring two and a half hours at Arthur Ashe Stadium to secure his victory.
"Just hanging in there, trying to create my own pace and control the rallies," Djokovic said about dealing with the capable and aggressive game of Seppi.
"It was a tough three sets."
Venus Williams, who won the second of her two U.S. Open titles 14 years ago, struck a blow for the older set and stayed on course for a quarter-finals collision with Grand Slam-seeking sister Serena by taming Swiss teen Belinda Bencic 6-3 6-4.
Venus, 35, produced a vintage power-game performance to beat the up-and-coming 18-year-old in a match-up between the oldest and youngest players left in the women's draw.
Williams, who played her first U.S. Open in 1997, the year 12th-seeded Swiss was born, had battled to a pair of three-set wins and spent nearly five hours on court to reach the third round.
However, the American made quick work of Bencic, who beat 2015 Australian, French and Wimbledon champion Serena Williams on her way to winning in Toronto last month.
"I just wanted to stay aggressive and keep my errors down," said Venus, who had also beaten Bencic in straight sets in their three previous encounters.
Joining the seven-times grand slam singles winner in the fourth round was Russian 13th seed Ekaterina Makarova, who advanced with 6-3 7-5 victory over 17th seed Elina Svitolina of Ukraine.
(Editing by Mark Lamport-Stokes)