Top seed and tennis world No.1 Novak Djokovic notched another straight sets win but was given a workout in his 6-3 7-5 7-5 victory over Italian Andreas Seppi in reaching the fourth round at the US Open.
Djokovic had lost just 10 games through the first two rounds and despite beating 25th-ranked Seppi in all 10 of their previous meetings, the 28-year-old needed a tiring two and a half hours at Arthur Ashe Stadium to reach the Round of 16.
The Serb can be excused for lighting up in anticipation when facing an Italian opponent after registering 30 successive victories against Italians.
But the 31-year-old Seppi gave Djokovic some difficulty.
"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."
Djokovic had not faced a single break point in his first two matches, but Seppi earned one in the third game of their third-round encounter and cashed in.
But Djokovic broke right back and was on his way to victory in his easiest set of the match.
Serving for the match at 5-4 in the third set, the Serb was broken again, but Djokovic broke right back in the next game and completed his victory after fighting off two break points in the final game.
"Satisfied, but you can always do better," said Djokovic, about his victory over Seppi, who ousted Roger Federer in the third round of the Australian Open this year.
"A win is a win. He is 25 in the world for a reason."
Djokovic will next play either 14th seed David Goffin of Belgiuim or Spain's Roberto Bautista Agut.
Meanwhile reigning champion Croatian Marin Cilic kept his title defence on track but not without a scare as the ninth seed needed over four hours to put away Kazakthstan's Mikhail Kukushkin and reach the fourth round with a 6-7 7-6 6-3 6-7 6-1 win.
Cilic stepped onto the Grandstand court having won 16 straight sets at Flushing Meadows but that string quickly came to an end when the 56th-ranked 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."
In the women's draw Venus Williams avenged a rare loss suffered by top-ranked sister Serena and dispatched a Swiss foe just like old times in New York by defeating Swiss player Belinda Bencic.
The 35-year-old American, a seven-time Grand Slam champion, ripped Bencic 6-3 6-4 to reach a fourth-round matchup with Estonian qualifier Anett Kontaveit and eliminate the top-ranked rival on Serena's side of the US Open bracket.
Bencic defeated Serena last month in a Toronto semi-final on her way to the title and Venus, who improved to 4-0 all-time against Bencic, received some guidance from her younger sister on how to handle the 18-year-old.
"That's between us," Venus said when asked about specifics. "I think it worked."
Venus was equally coy when asked if the triumph was sweeter given Bencic's victory over Serena.
While evading the question, she didn't say no.
"Whoever is across the net, I want to win," Venus replied.
"Whoever that person is, that's the day I want to win."