Flawless Serena storms into quarters

NEW YORK (AP):Serena Williams didn't drop a game in advancing to the quarter-finals of the United States (US) Open. Roger Federer moved on with even less work when Mardy Fish pulled out of their fourth-round match yesterday for precautionary reasons.

Fish missed about two months this season because of an accelerated heartbeat and had a medical procedure in May. His agent, John Tobias, said "we are not 100 per cent sure what the issue is and if it is related to his previous issues".

"I was reluctant to do so, but am following medical advisement," Fish said about his withdrawal in a statement. "I had a good summer and look forward to resuming my tournament schedule in the fall."

The 30-year-old American's third-round match against Gilles Simon went five sets, lasting more than three hours and ending after 1 a.m. yesterday. Afterward, the 23rd-seeded Fish did not appear at a news conference. Tournament officials said he was getting treatment, but didn't give specifics.

"I am really sorry for Mardy. I just want to wish him a speedy recovery," Federer said in a statement. "We all want to see him back on tour soon."

'double bagel'

Williams beat 82nd-ranked Andrea Hlavackova 6-0, 6-0 in 57 minutes. It was the first time in 62 career victories at Flushing Meadows that the three-time US Open champion enjoyed a 'double bagel'.

"She was fighting really hard," Williams said. "You give people any type of chance, especially in tennis, the match is never over until you shake hands. There is always a comeback available. So I didn't want to give her that opportunity - or anyone that opportunity - to try to come back, especially her in particular. She was getting so pumped up and she never gave up. I thought that was really incredibly positive."

Williams had 31 winners and just seven unforced errors. She and sister Venus played doubles last night in Arthur Ashe Stadium.

Williams will next face Ana Ivanovic, who is finally back in a Grand Slam quarter-final more than four years after her French Open title.

The 12th-seeded Serb beat Tsvetana Pironkova 6-0, 6-4.

Ranked No. 1 in the world in 2008, Ivanovic has struggled with injuries and her confidence since.

"There were some good moments and some tough ones, but it's a process. I understand it better now," she said. "There are times when you realise that it's exactly what it is: It's a process. You can't have everything at the same time. You have to be consistent on practice courts and then in the matches."

After failing to serve out the match at 5-3 in the second set, Ivanovic broke the 55th-ranked Bulgarian at love in the next game to clinch the victory.

Sara Errani, seeded 10th, beat sixth-seeded Angelique Kerber 7-6 (5), 6-3.

Federer, in his 34th consecutive quarter-final at a major tournament, will meet sixth-seeded Tomas Berdych, who defeated 11th-seeded Nicolas Almagro 7-6 (4), 6-4, 6-1 in two hours.

"At least good that I didn't stay that long on court, that I was able to save some energy, as well," Berdych said.