Serena Williams wins in 49 minutes

NEW YORK -- 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 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.

How hard 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 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.

"Did you guys see the match? Or was it too quick?" Krajicek asked reporters.

"Sometimes when you're on the court against her, you just think, 'OK, she misses a few balls.' ... But she doesn't miss a lot. It's just tough to keep the same level as her," said Krajicek, the younger sister of 1996 Wimbledon champion Richard Krajicek. "I mean, nobody hits as hard as her. Nobody. Not even her sister."

Venus, who won the U.S. Open in 2000 and 2001, said in an interview Thursday with ABC's "Good Morning America" that she "absolutely" plans to return to tennis and is relieved, after years of misdiagnosis, to know exactly what's been making her feel "debilitating" fatigue.

"I know she's a fighter, and she's really strong. She's great," Serena said. "I think she's really happy now that she knows what it is, after all this time."

While no one was surprised to see the 28th-seeded Serena move on -- her ranking dropped after she missed nearly a year with her own series of health scares -- she was joined by a 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, before flying back that night and playing 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 before rolling 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."

Serena, meanwhile, will take 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."

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 Falconi taking on No. 22 Sabine Lisicki of Germany.

In other action Thursday, seventh-seeded Francesca Schiavone needed just 53 minutes to advance to the third round, beating Mirjana Lucic 6-1, 6-1.

The 2010 French Open champion had only one double-fault after committing 16 in her three-set first-round victory.

Schiavone did not face a break point and had only seven unforced errors, compared with 32 for Lucic.

The 96th-ranked player from Croatia, a former teen sensation, hasn't reached the third round at a Grand Slam tournament since 2001.

Schiavone will next face unseeded Chanelle Scheepers of South Africa, a 6-4, 7-5 winner over Mona Barthel of Germany.

Jelena Jankovic also won in straight sets despite needing an injury timeout early in her second-round match against Jelena Dokic.

The 11th-seeded Serb won 6-3, 6-4 in 1 hour, 21 minutes. She said her back started feeling stiff early in the opening set. She hadn't had any problems with it before Thursday.

A trainer also worked on her lower back after she won the first set.

Jankovic hasn't advanced past the third round at Flushing Meadows since 2008, when she lost to Williams in her only Grand Slam final.

The 73rd-ranked Dokic withdrew from three tournaments after Wimbledon with a hamstring injury. The Australian had 15 double-faults in nine service games Thursday, getting broken six times. Jankovic was broken four times.

In other results, No. 10 Andrea Petkovic of Germany rallied past Zheng Jie of China 3-6, 6-3, 6-3; 15th-seeded Russian Svetlana Kuznetsova beat Elena Baltacha of Britain 6-4, 6-3; No. 17 Anastasia Pavlyuchenkova of Russia held off Croatia's Petra Martic 6-4, 2-6, 6-4; 18th-seeded Roberta Vinci of Italy defeated Alize Cornet of France 6-2, 6-3; and
Silvia Soler-Espinosa of Spain upset No. 31 Kaia Kanepi of Estonia 6-4, 6-2.

Information from The Associated Press was used in this report.