NEW YORK (WFAN/AP) — Neither her words nor her play indicated that Serena Williams was distracted one bit Thursday at the U.S. Open.

She would have been forgiven if they had, of course, given that her older sister Venus withdrew from the tournament 24 hours earlier and revealed a recently diagnosed immune system disease.

Focused as ever, Serena absolutely overwhelmed Michaella Krajicek of the Netherlands 6-0, 6-1 to reach the third round, showing precisely why many consider her the favorite to win a fourth championship at Flushing Meadows and 14th Grand Slam title overall.

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How was it to set aside Venus’ situation?

“It really wasn’t that difficult, to be honest. I mean, she wants me to do the best; she wouldn’t want me to suffer,” Serena said. “So now, if anything, it should motivate me more.”

If that’s so, look out. She’s lost three games in two matches this week. She’s won 14 matches in a row and 29 of her last 30 on hard courts. On Thursday, she hit 10 aces, erased the only break point she faced, compiled a 25-5 edge in winners and made only 10 unforced errors in a powerful display that lasted all of 49 minutes.

Now Serena figures to face a sterner test on the court Saturday than Krajicek presented, taking on No. 4 Victoria Azarenka, who beat Gisela Dulko of Argentina 6-4, 6-3.

“As people say: To win the U.S. Open, you have to beat top players. It doesn’t matter when and where,” said Azarenka, a semifinalist at Wimbledon. “To sit and complain, ‘Oh, my God, I got her in the third round?’ No. I have to go out there, compete and try to beat her.”

While no one was surprised to see the 28th-seeded Serena move on — her ranking fell after she missed nearly a year with her own series of health scares — she was joined by a larger-than-lately contingent of countrywomen. Two Americans ranked outside the top 100, 18-year-old Sloane Stephens and 21-year-old Vania King, knocked off seeded players to give the host country five women in the third round for the first time since 2004, when eight made it.

“We’re ready to go to the top, baby,” a smiling Stephens said, clapping three times for emphasis.

The 106th-ranked Stephens, who lives in California, beat 23rd-seeded Shahar Peer of Israel 6-1, 7-6 (4). Stephens, who hit one ace at 119 mph, never won a Grand Slam match until this week, is the youngest woman left in the draw, and already has plans for her prize money.

“Now I know for sure when I get home after the season’s over, I’m getting a car. That’s the only thing I’m really looking forward to now,” she said. “My mom wants me to get a truck. I want to get a small car. It’s very confusing.”

Two years ago, when she was 16 and playing in the U.S. Open junior tournament, Stephens left New York to attend the funeral of her father, 1988 NFL Offensive Rookie of the Year John M. Stephens, in Louisiana, then flew back that night and played a match the next morning.

“The emotions and everything was crazy,” Stephens said. “For me, today was really crazy, as well. But it’s totally different.”

The 103rd-ranked King, a 22-year-old who splits time between Florida and California, eliminated No. 29 Jarmila Gajdosova of Australia 6-2, 6-0.

Now things get even tougher: For a spot in the fourth round, Stephens will face 2008 French Open champion and former No. 1 Ana Ivanovic of Serbia on Saturday, while King takes on current No. 1 Caroline Wozniacki of Denmark.

Ivanovic advanced when her opponent, Petra Cetkovska, withdrew because of a quadriceps injury. Wozniacki lost her serve in the opening game, then rolled off 12 of the next 13 to defeat Arantxa Rus 6-2, 6-0 on Thursday night.

“I’m American, so I know I’ll get some support out there,” King said. “But she’s No. 1 in the world, so she will, too.”

The other two American women are in action Friday, with 19-year-old Christina McHale meeting No. 25 Maria Kirilenko of Russia in Arthur Ashe Stadium at night, and 21-year-old Irina Falconi taking on No. 22 Sabine Lisicki, one of four Germans still in the field.

The highest-seeded U.S. man, No. 8 Mardy Fish, got to the third round for a third consecutive appearance in the U.S. Open by beating Tunisian qualifier Malek Jaziri 6-2, 6-2, 6-4.

“I haven’t really been tested that much. I can’t do anything about that,” said Fish, who has dropped 13 games through two matches. “I can’t do anything about who I come up against.”

Not much Dudi Sela could have done Thursday, eight. His task? Facing 16-time major champion Federer. The result? Federer won 6-3, 6-2, 6-2, taking 52 of 60 points on his serve.

“It’s tough to play him, especially when you’re not at your best and on center court,” Sela said. “On Court 25, maybe I’d have a bigger chance. I had no chance.”

Neither, it turned out, did half the players in Arthur Ashe Stadium on Thursday.

Will we see a US player take home one of the Open trophies? Sound off in the comments below…

(TM and Copyright 2011 CBS Radio Inc. and its relevant subsidiaries. CBS RADIO and EYE Logo TM and Copyright 2011 CBS Broadcasting Inc. Used under license. All Rights Reserved. This material may not be published, broadcast, rewritten, or redistributed. The Associated Press contributed to this report.)

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