Defending champion Rafael Nadal reached the US Open last 16 with a 7-6 (7/5), 6-1, 7-5 victory over gutsy close friend David Nalbandian on Sunday.
But it was an uneven performance from the second-seeded Spaniard who endured a first set hiccup, when he trailed the 76th-ranked Argentine 3-5, and was broken when he served for the match in the ninth game of the third.
Up next for the 10-time Grand Slam title winner is Gilles Muller of Luxembourg, who eased past Russia's Igor Kunitsyn 6-1, 6-4, 6-4, for a place in the quarter-finals.
"It was a tough day. David is a fantastic player and a close friend who has had a tough time with injuries," said Nadal.
"The first set was key when I came back when he was serving for the set. I am happy because I played my best match of the tournament so far."
Nalbandian, who reached three in the world in 2006 before his career was stalled by hip and groin surgery, went into the the tie on a muggy Arthur Ashe Stadium with a 2-2 career record against the Spaniard.
And he was far from unbowed in the opening set when a game plan of all-out attack, which witnessed 18 winners and 23 unforced errors, almost paid dividends before Nadal played a more composed tiebreak.
That gruelling effort took an immediate toll on the 29-year-old Nalbandian, who was broken three times in the second set.
Nalbandian stopped the rot with a surprise break in the opening game of the third, Nadal's concentration not helped by being hit with a time code violation by umpire Pascal Maria for taking too long between points.
The Spaniard, bristling at the decision, took out his frustrations by breaking back before immediately calling a medical time-out for treatment on his blistered right foot.
Nadal was another break to the good on his way to a 5-2 lead before the dogged Nalbandian clawed back to 5-5, boosted by a break when the world number two served for the match at 5-3.
But the second seed held for 6-5 and claimed victory in the 12th game when Nalbandian, whose final error total climbed to 60, served up a seventh double fault.
Later Sunday, British fourth seed Andy Murray, the 2008 runner-up, takes a 5-0 career record into his third round clash with Spanish left-hander Feliciano Lopez.
The winner of that tie will face either Argentine 24th seed Juan Ignacio Chela, a 2007 quarter-finalist, or American wildcard Donald Young, a former world junior number one bidding to reach the last 16 of a Grand Slam for the first time.
Argentine 18th seed Juan Martin del Potro, the 2009 champion, faces French 12th seed Gilles Simon while 2003 winner Andy Roddick, the American 21st seed, takes on French wildcard Julien Benneteau.
The day's other third round matches sees an all-American clash between 28th seed John Isner and Alex Bogomolov while Spanish fifth seed David Ferrer, a semi-finalist in 2007, meets German 26th seed Florian Mayer.