World number one Novak Djokovic weathered a first-set storm to subdue Alexandr Dolgopolov 7-6 (16/14), 6-4, 6-2 on Monday and reach the quarter-finals of the US Open.

Djokovic set up an all-Serbian last-eight clash with Davis Cup teammate Janko Tipsarevic, but first he had to quell the challenge presented by world number 23 Dolgopolov on the windy Louis Armstrong Stadium.

Djokovic, who has lost just two matches this year and claimed the Australian Open and Wimbledon titles as he surged to the top of the rankings, needed six set points -- and had to save 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 around the court and an array of shots to wrong-foot Djokovic.

"It was strong wind, tricky conditions, he's the kind of player who knows how to play in these conditions," said Djokovic after his 61st win of the year.

"I was confused on the court the first set, but it was really exciting -- really exciting."

Two straight forehand errors from Djokovic gave Dolgopolov a 4-0 lead in the decider, but the Serbian roared back to win the next five before Dolgopolov gave himself a set point at 6-5 that Djokovic saved with a forehand winner.

Djokovic saved another set point before having one of his own, which Dolgopolov saved with an awkward volley that Djokovic was sure was wide.

Djokovic's next two chances came against Dolgopolov's serve, and the Ukrainian saved one with an ace before Djokovic gave himself another on his own serve at 12-11.

A rally featuring Dolgopolov's save of a net-cord bounce ended with Djokovic's defensive lob landing just long for 12-12. Each wasted another set point before Dolgopolov sent a forehand long to end it.

From there Djokovic was in control, opening each of the next two sets with service breaks and rolling home from there.

He said it would be difficult to play his Davis Cup teammate 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.

After the first three sets averaged more than an hour apiece, the fourth set lasted barely more than half that as Tipsarevic pulled away from the flagging Ferrero.

"He ran out fuel in his tank," Tipsarevic said, noting that Ferrero opened the tournament with two five-set matches.

"I feel that that in the third set, apart from me playing and serving extremely well, I feel that that was kind of an issue," Tipsarevic said.

In other last 16 matches, third-seeded Roger Federer, seeking to stretch a streak of eight straight years with at least one Grand Slam crown, tackled Argentinian Davis Cup stalwart Juan Monaco and eighth-seeded Mardy Fish, the top American in the men's field, took on flamboyant Frenchman Jo-Wilfried Tsonga.