Ohio - World number one Rafael Nadal saved a match point and rallied to defeat France's Julien Benneteau 5-7, 7-6 (8/6), 6-2 to reach the quarter-finals of the three million-dollar ATP Cincinnati Masters.
The reigning Wimbledon and French Open champion from Spain won for the 36th time in his past 38 matches but was on the verge of being ousted in the tie-breaker before fighting back.
"A match like this gives me a lot of confidence," Nadal said. "It's important for everything. A match point? Yeah. I am doing this well. I am playing aggressive. But I need to do better the next few days."
Nadal reached a quarter-final against Cypriot Marcos Baghdatis, who upset Czech seventh seed Tomas Berdych 7-5, 6-4.
"He's a very tough player," Nadal said of Baghdatis. "It will be a very good match."
World number two Roger Federer, fourth-ranked Briton Andy Murray and Serbian second seed Novak Djokovic also advanced with triumphs on Thursday.
The four top seeds reached the semi-finals last week at Toronto, a feat that could be repeated in Cincinnati.
Nadal was given all he could handle by Benneteau, who broke Nadal twice to take the first set and nearly stopped the Spaniard in the 12th game of the second set before the top seed reached the tie-breaker.
Nadal jumped to a 4-1 lead but a pair of aces by Benneteau gave the Frenchman a match point at 6-5. Nadal won the next three points to force a third set, prompting both men to seek help from the trainer - Nadal for tape on his right foot and Benneteau to combat cramping.
Benneteau suffered a left leg cramp again two points into the third set, surrendered a break at love and sought treatment only to learn he had to wait for another changeover. By then it was 3-0 for Nadal.
Nadal surrendered a break in the next game but broke back to 4-1 and held from there to finish off the test after two hours and 48 minutes when Benneteau sent a backhand beyond the baseline.
"It wasn't easy for sure," Nadal said. "Julien played a good match. At the beginning he played at a high level. I made a few mistakes. I have to keep improving."
Defending champion Federer had the easiest day, reaching the final eight by walkover when Germany's Philipp Kohlschreiber pulled out of their scheduled third-round match with a right shoulder injury.
The 16-time Grand Slam champion from Switzerland has not yet finished a set in the $3m hard-court event after a first-round bye and a 5-2 lead when Uzbek qualifier Denis Istomin retired with an injury on Wednesday.
Federer will next meet Russian sixth seed Nikolay Davydenko, who beat Spain's David Ferrer 4-6, 6-3, 7-5.
Third-ranked Djokovic defeated Argentina's David Nalbandian 6-1, 7-6 (9/7) and will next face American Andy Roddick, who outlasted Swedish fifth seed Robin Soderling 6-4, 6-7 (9/7), 7-6 (7/5).
Nalbandian, who won two weeks ago at Washington, double-faulted on match point to hand Djokovic the victory and suffer just his second loss in 11 tie-breakers this year.
Murray advanced by outlasting Latvia's Ernests Gulbis 4-6, 6-3, 7-6 (7/4).
The 23-year-old Scotsman won six of nine break-point chances and made only 23 unforced errors while benefitting from 54 from Gulbis in booking a spot in the final eight.
"I was struggling a little bit but I managed to save it," Murray said. "I hung in there well. He had chances in the second set. I was struggling with my legs a little bit in the third set. I was tired but I hung in there."
Murray, who won on his fourth match point after seizing a 6-1 lead in the tie-breaker, will next face American Mardy Fish, who ousted Frenchman Richard Gasquet 7-5, 6-2.
"He plays aggressive tennis," Murray said of Fish. "I will have to hit my passing shots and take advantage of my opportunities."
Murray is coming off a title last week at Toronto, where he beat Nadal and Federer in the last rounds, becoming only the fifth man to oust both on his way to a title.
Murray improved to 6-10 in tie-breakers for the year and dropped Gulbis to 11-5, but what looked to be an easy tie-break romp proved tougher by the end, which came after two hours and 33 minutes.
Gulbis netted a forehand to give Murray a 3-0 lead and sent an overhead smash into the net to hand the Scotsman a 4-1 lead on the way to dropping six of the first seven points.
The Latvian pulled back three match points before sending a forehand long to give Murray the victory despite hitting 49 winners to only 22 for the Briton.