NEW YORK: Just when the US Open is getting down to the crucial matches, world number one Novak Djokovic found himself in a flawless zone that even he rarely reaches to put himself in a quarter-final matchup.

The six-time Grand Slam champion from Serbia routed Spain's 43rd-ranked Marcel Granollers 6-3, 6-0, 6-0 in only 79 minutes at Arthur Ashe Stadium.

“It's a great joy,” Djokovic said. “It's a fantastic feeling when you're playing this well. You love spending time on the court and experiencing such a great zone where you are at that moment.”

Djokovic won the first 25 points on his serve in the match, won the final 15 games and faced his only break point in the last game on the way to his 18th consecutive Grand Slam quarter-final appearance.

“I definitely played one of the better matches that I've played in my life here at Arthur Ashe,” Djokovic said.

“It was 3-all in the first set and then I managed to get the right advantage and I played flawless tennis.

“I had everything working, every part of my game. This is great encouragement going into the next round.”

Djokovic, who won the 2011 US Open title, will play for a semi-final berth against Russian 21st seed Mikhail Youzhny, a two-time US Open semi-finalist who ousted Australia's Lleyton Hewitt in five sets after four hours.

Granollers came into the Djokovic match after four five-set triumphs.

“Probably pays its toll, the fact they have played five-setters and they are coming in tired in the matches,” Djokovic said.

“But I really don't try to pay attention to my opponents during the matches. I have this very determined vision of what I need to do on the court.

“My goal is to win the matches whoever I play against.”

Djokovic, seeking his fourth consecutive trip to the US Open final, said that he had never dominated anyone so completely with his serve as he did in overwhelming Granollers at the start of the match.

“This is probably the first time I've experienced something like that,” Djokovic said.

“I can't say I have one of the strongest serves on the tour but I served pretty well.”

Asked if could have played any better after splitting the first six games of the match, Djokovic said, “Well, I haven't dropped a game from that moment, so I think the result says how well I played.”

“As the match progressed I played incredibly well and at a very high level.”

“I had some great matches in the past that I can compare with this one, but definitely the second and third set have been some of the best tennis that I've played on Arthur Ashe.”

That includes his 2011 final triumph over Rafael Nadal and an epic five-set loss to Britain's Andy Murray in last year's final.

And it certainly comes at a good time, with potential matches against Murray in the semi-finals and Nadal in Monday's final.

“It all comes at a great time for me,” Djokovic said.

“I was wishing to be more aggressive as the tournament progresses and to be able to stay committed to play every point, to win every point, regardless of what's the score.

“So I'm very happy with my mental state, how I feel physically, and the way I played. It's definitely coming at the best possible time.”

Djokovic captured his fourth career Australian Open title this year, lost to Murray in the Wimbledon final and fell to Nadal in a French Open semi-final.

Djokovic, 26, has not dropped a set on the New York hardcourts as he booked a date in the US Open last eight for the seventh year in a row.