New York - World number one Novak Djokovic set up an all-Serbian quarter-final at the US Open on Monday, surviving a marathon tiebreaker en route to victory over Alexandr Dolgopolov.
Djokovic, who has lost just two matches in a spectacular season that has seen him win the Australian Open and Wimbledon as he surged to number one, triumphed 7-6 (16/14), 6-4, 6-2 to advance to a last-eight meeting with friend and Davis Cup teammate Janko Tipsarevic.
France's 11th-seed Jo-Wilfried Tsonga doused the hopes of eighth-seeded American Mardy Fish with a 6-4, 6-7 (5/7), 3-6, 6-4, 6-2 victory, setting up a possible Grand Slam rematch with third-seeded Roger Federer.
Five-time US Open champ Federer didn't take the court in the Arthur Ashe Stadium for his fourth-round match against Argentinian Juan Monaco until shortly before midnight, thanks to a protracted battle between women's world number one Caroline Wozniacki and former champion Svetlana Kuznetsova.
The start of that match had already been delayed by Tsonga's tussle with Fish in which both players struggled with swirling winds.
Tsonga gained the upper hand for good with a service break in the ninth game of the fourth set and then closed it out with a love game.
Fish, who had treatment on his troublesome right hip and thigh after the set, had no answer as Tsonga took a 5-1 lead in the fifth and sealed victory with an overhead on his third match point.
"Today was just really difficult because of Mardy, of course, because of the wind, because of all the conditions. I was mentally strong," said Tsonga, who rallied from two sets down to stun Federer in the quarter-finals at Wimbledon.
For Fish, playing his first Grand Slam as America's top-ranked man, it was a bitter pill to swallow after a hardcourt victory and two finals appearances in the build-up to the US Open.
Djokovic, playing out on the smaller Louis Armstrong Stadium, struggled with the wind and with the unpredictable Dolgopolov in the early going, needing six set points - and saving four - to claim the first-set tiebreaker.
Dolgopolov, a 22-year-old Ukrainian enjoying the best year of his career, showed no fear against tennis' dominant player, using his speed and a variety of pace to keep Djokovic on the hop.
"I was confused on the court the first set," admitted Djokovic, who nevertheless notched his 61st match victory of the year with relative ease.
"I think it was exciting for the crowd to watch because it was very close," he said. "But I think it was game-wise an ugly first set because I wasn't happy with the way I played.
"He was changing pace a lot. He was always sending me a different ball. It was really hard for me to adjust to it because of the conditions that we played in."
Ugly or not, the packed house loved it, and Djokovic said he was happy to play a match on the more intimate Armstrong court.
"It was a different experience because I haven't played on that court for a while," Djokovic said. "Sometimes it's really nice to be on the smaller court where the crowd is closer to the court where you can feel them."
Two straight forehand errors from Djokovic gave Dolgopolov a 4-0 lead in the tiebreaker.
A favorable net cord helped Djokovic take the next point to launch a run of five straight, and he finally finished it off when Dolgopolov sent a forehand long.
From there Djokovic was in control, opening each of the next two sets with service breaks and rolling home from there.
"He wore me out," Dolgopolov said. "I gave a bit of a fight, but I still need some work."
Djokovic said it would be difficult to play Tipsarevic in the quarter-finals, but the match-up has an upside.
"There's going to be a Serbian in the semi-finals, which is great for our country," he said.
Tipsarevic, 27, reached the last eight of a Grand Slam for the first time, prevailing in a baseline battle against former world number one Juan Carlos Ferrero 7-5, 6-7 (3/7), 6-5, 6-2.
Twenty aces made the difference for Tipsarevic, the last coming on his first match point against the 31-year-old Spaniard who has been slowed by a litany of injuries and fallen to 105 in the world.
The quarter-final lineup will be completed on Tuesday, when defending champion and second seed Rafael Nadal takes on unseeded Gilles Muller of Luxembourg and world number four Andy Murray tackles young American Donald Young.
Fifth-seeded David Ferrer of Spain faces America's former world number one Andy Roddick, and French 12th seed Gilles Simon meets big-serving American John Isner.