Serena barely works up a sweat

It took 49 minutes of Serena Williams' time Thursday to advance to the third round of the U.S. Open. It's likely she warmed up longer than that.

Williams hustled Michaella Krajicek out of Arthur Ashe Stadium with a 6-0, 6-1 nanosecond victory. It was the most visible win of a strong afternoon for American women's tennis. California teenager Sloane Stephens defeated No. 23 seed Shahar Peer, 6-1, 7-6 (4), and Vania King ousted No. 29 seed Jarmila Gajdosova, 6-2, 6-0. With Irina Falconi and Christina McHale winning Wednesday, that's five American women through to the third round.

Her sister Venus' withdrawal from the Open with an autoimmune disease isn't sapping any energy out of Serena's comeback. The foot injury from last year and the pulmonary embolism from this year are being put well behind her as she motors through the hard-court season. She had two hard-court wins this summer at Stanford and Toronto and comes into this tournament with fitness, and now with Venus in mind.

"She wants me to do the best; she wouldn't want me to suffer," Serena said when asked if her sister's condition weighs on her. "So now, if anything, it should motivate me."

Stephens, 18, has found motivation from the Williams sisters, who are a generation ahead of her. "Awesome players, awesome girls," said the effervescent Stephens. "They changed the sport of tennis. They changed women's sports in general. An inspiration to all girls that play sports. With Venus gone, that's definitely upsetting. But Serena here dominating again, I think that's really good to have her back and it's awesome for women's sports."

This is Stephens' best performance in a Slam and really the best performance of a budding career that included a win earlier this year over Julia Goerges at Carlsbad.

"I definitely felt that I was ready for this," Stephens said. "I knew what I could do. I knew if I stayed positive and focused, I would be able to come out with some good stuff in the end."

No. 1 seed Caroline Wozniacki brushed by Arantxa Rus, 6-2, 6-0, Thursday night. She will play King next. Stephens gets Ana Ivanovic next. Williams will play No. 4 seed Victoria Azarenka, a 6-4, 6-3 winner over Gisela Dulko.