(CNN) -- Serena Williams underlined her status as the overwhelming favorite for the women's U.S. Open title with a crushing "double bagel" win over Carla Suarez Navarro in the quarterfinals of the New York grand slam.
The defending champion, bidding for a fifth singles triumph at Flushing Meadows, beat the Spanish world No. 20 6-0 6-0 to become the first woman since Martina Navratilova in 1989 to win a women's U.S. Open quarterfinal without losing a game.
"I played well -- I played really well," world No. 1 Williams told the WTA's official website. "I was just more focused than anything.
"I like to believe there is always room for improvement though. I haven't really thought about it yet, but off the bat, I think it was very difficult to hit a big serve today because of the winds, and I didn't get my serve up as much as I wanted to. But I don't know. I do think I definitely played well tonight."
The American's latest commanding win means she has lost just 13 games at the tournament ahead of her semifinal meeting with Li Na, who is appearing in the last four of the year's final grand slam for the first time after beating Russia's Ekaterina Makarova.
"I'm still in the tournament and I'm not thinking like, 'I'm really dominant now'," added Williams. "I'm thinking I have a really tough match in the next round and want to do well."
Earlier in the day second seed Victoria Azarenka, beaten by Williams in the 2012 final, won her delayed fourth round match against former world No. 1 Ana Ivanovic.
In the men's draw, top seed Novak Djokovic made light work of his fourth round meeting with Spaniard Marcel Granollers.
The six-time grand slam champion wrapped up a 6-3 6-0 6-0 win in just one hour and 19 minutes.
The world No. 1 was delighted with his performance as he bids to erase the memory of an agonizing five-set defeat to Andy Murray in last year's final.
"I had some great matches in the past that I can compare with this one today, but definitely today, second and third set have been some of the best tennis that I've played on Arthur Ashe in my career," Djokovic told the ATP Tour's official website.
"It's a fantastic feeling when you're playing this well. You love spending time on the court and experiencing such great zone where you are at that moment."
Djokovic's quarterfinal opponent will be 21st seed Mikhael Youzhny, who got the better of 2001 champion Lleyton Hewitt in a marathon five-set contest.
Defending champion and second seed Murray survived a scare to set up a last eight match with Swiss No. 9 Stanislas Wawrinka.
The Briton lost the first set of his meeting with Uzbekistan's Denis Istomin before roaring back to clinch a 6-7 (5-7) 6-1 6-4 6-4 victory.
"I wanted to just try and get through the match," said 2013 Wimbledon winner Murray. "In the end it was difficult conditions. It was extremely windy today.
"With the way he plays, he hits the ball pretty big and flat on both sides, strokes pretty low, hard at times to control. He made it very difficult for me.
"With the way the third set ended up going, I was just very happy to get it done, because he had chances at the end of the third set to go ahead."