US Open 2014: Novak Djokovic and Serena Williams progress

Novak Djokovic is expecting a tough quarter-final against Andy Murray

Top seed Novak Djokovic reached his 22nd consecutive Grand Slam quarter-final with a straight-sets win over Philipp Kohlschreiber at the US Open.

The world number one secured a 6-1 7-5 6-4 victory over the German and will next play Andy Murray after the Briton beat Jo-Wilfried Tsonga 7-5 7-5 6-4.

Third seed Stan Wawrinka beat Spain's Tommy Robredo 7-5 4-6 7-6 (9-7) 6-2.

In the women's singles, defending champion Serena Williams set up a last-eight meeting with Flavia Pennetta.

Williams, 32, beat Estonia's Kaia Kanepi 6-3 6-3 in 65 minutes.

The victory keeps Williams on course to become only the second woman to win three consecutive US Open titles since the Open Era began in 1968.

It is the first time Williams, a five-time champion in New York, has reached the quarter-finals of a Grand Slam this year.

Pennetta, the 11th seed, beat Australian Casey Dellacqua 7-5 6-2 to reach the last eight in New York for the fifth time in seven years.

Were Williams to win the title for a third straight year, she would emulate compatriot Chris Evert, who won the US Open four times in succession from 1975 to 1978.

Serena Williams has not lost more than three games in any set

Japan's Kei Nishikori beat fifth seed Milos Raonic in a five-set men's singles encounter that equalled the record as the longest match ever at the US Open.

It took the 10th seed four hours and 19 minutes to record a 4-6 7-6 (7-4) 6-7 (6-8) 7-5 6-4 victory over the Canadian, matching the time of a 1993 match between Swedes Mats Wilander and Mikael Pernfors and the third-round tie between Germany's Philipp Kohlschreiber and John Isner of the United States in 2012.

Nishikori will face third seed Wawrinka of Switzerland in the quarter-finals.

Arthur Ashe Stadium

Flavia Pennetta (Ita) (11) beat Casey Dellacqua (Aus) 7-5 6-2

"Everyone asks the same question," said Pennetta, 32, when asked to explain her success after reaching her fifth US Open quarter-final. "I don't know. I just like to play here and maybe that's why I play good here."

"When you are young, you want it too badly to have something. So much pressure. When you are a little bit old, you see things in a different way. I mean, tennis is important, but life is important. Family is important. So you're starting to have the good balance for everything."

Serena Williams (US) (1) beat Kaia Kanepi (Est) 6-3 6-3

"I never thought it would be so exciting," Williams said on reaching her first Grand Slam quarter-final of 2014.

"Yeah! It feels good. Obviously I don't want this to end. But I'm just happy that I'm able to be performing a little better at the end of the year."

Andy Murray (GB) (8) beat Jo-Wilfried Tsonga (Fra) (9) 7-5 7-5 6-4

Report

Kei Nishikori (Jpn) (10) beat Milos Raonic (Can) (5) 4-6 7-6 (7-4) 6-7 (6-8) 7-5 6-4

"I was down 2-1 in the third and it was really tight and it was really tough," Nishikori, 24, said of his epic encounter with the 6ft 5in Canadian.

"He had a great serve - I just tried to play one point at a time and keep fighting."

Victoria Azarenka (Blr) (16) beat Aleksandra Krunic (Ser) 4-6 6-4 6-4

"Alexandra played some amazing tennis," said Azarenka on her diminutive rival debuting on Arthur Ashe. "She has a great future. It's never easy to play somebody you don't know. She stepped it up and I just tried to stay positive and fight and do anything I could to turn the match around."

Louis Armstrong Stadium

Novak Djokovic (Ser) (1) beat Philipp Kohlschreiber (Ger) 6-1 7-5 6-4

"I think it's great that I have been playing some really good tennis, really high quality so far, but it's normal to expect that I'm going to have tougher opponents as the tournament goes on," said Djokovic. "You know, quarter-finals against Murray, it's a very tough draw. It's the way it is."

Ekaterina Makarova (Rus) (17) beat Eugenie Bouchard (Can) 7-6 (7-2) 6-4

Bouchard had her blood pressure taken during a medical timeout on a sweltering New York day

"I was feeling very light-headed and dizzy on the court, just seeing things a little blurry," said Bouchard. "Feeling well physically on the court is very important to me. I just generally didn't feel good.

"I think it developed as the match went on. In the middle of the first set I started not feeling great. But I have had a few late, tough matches here, and I don't think I fully recovered from those. I was feeling it a little bit yesterday as well. I think that's what happened a little bit."

Makarova added: "I thought, thanks, because I also was tired. It was really a help for me also because I had some time to recover and also to use some ice bags. It was actually kind of good medical time-out."

Stan Wawrinka (Sui) (3) beat Tommy Robredo (Spa) (16) 7-5 4-6 7-6 (9-7) 6-2

Robredo on a verbal exchange between the Spaniard and the Swiss: "It's something that can happen in a match. I think he did something not nicely, and I just told him if he had a problem today. But that's it, nothing to talk about."

Wawrinka added: "I have no problem with him. It's always the same when you play a tough match. You always try to find solution how to win. He did a few things that I did not like, but at the end of the day it's a tennis match. What happens on the tennis court, you have to keep it there. I think it's all OK."

Monday's full results

Britwatch

Andy Murray might be through to the quarter-finals but his good friend Ross Hutchins has already gone one better and reached his first Grand Slam semi-final.

The Briton and partner Yung-Jan Chan of Taiwan progressed in the mixed doubles when Kveta Peschke had to retire, trailing 6-3 1-2 alongside Poland's Marcin Matkowski.

"It's exciting," said Hutchins. "It's the first one for me. I'm really pleased to be able to win a few matches. It's a shame for Kveta today. I didn't know she got injured. I knew she had an epic women's doubles match, and in that heat today, I don't know if I would have walked on the court let alone played a set and a half because it was roasting."

Ross Hutchins, with mixed doubles partner Yung-Jan Chan, said the New York heat was "roasting" during their match

Quotes of the Day

"We need a little time apart. He's been annoying lately. He cries. I think he's talking to me and I don't quite understand him. It's really stressing me out a little bit. I had to send him to his auntie's room yesterday to give me a little break." Serena Williams on Chip, her dog.

Andy Murray explains his apparent discomfort in the second set against Jo-Wilfried Tsonga. "I maybe went a little bit overboard with how much I was drinking at a few of the change of ends, at the beginning of the second set. Then after I went to the toilet the end of the second set I felt a bit better."

After Murray was given the Will Ferrell treatment over his lack of fashion sense, Jo-Wilfried Tsonga justifies his unique tucked-in top look: "I'm just sweating a lot, so my shirt is after two games, it's heavy, you know. It's like two kilograms, and when it's move like this (side to side) it disturbed me. That's why I always put the T-shirt in the short."

Aleksanrda Krunic is asked if she knows how much money she has won this week (US$187,300): "No. I know it's 30% tax. That makes me very sad. But the rest, I have no idea."

Wawrinka dived into the stand needed treatment - and later retweeted a picture. He said: "It was crazy a little bit when I arrived in the stand, because it never happened to me. It was quite a bad fall. But I'm lucky it didn't have any big problem with that. I was already struggling physically, so was nothing from the fall. I think I was quite lucky with that."