Serena, Djokovic, Nadal seek US Open last 16 spots

History-chasing Serena Williams tries to recover from a poor serving performance and reach the US Open fourth round on Friday while Novak Djokovic and Rafael Nadal also seek last-16 berths.

Three-time defending champion Williams has won her past 30 Grand Slam matches, completing a "Serena Slam" by taking four major titles in a row, and could add to her legend even more in the Flushing Meadows fortnight.

The 33-year-old American, who faces compatriot Bethanie Mattek-Sands in a third-round night match at Arthur Ashe Stadium, could complete the first calendar Grand Slam since Steffi Graf in 1988.

Williams would also collect her 22nd career Grand Slam singles crown, matching Graf's Open Era record and moving two shy of equaling Australian Margaret Court's all-time record.

But first she has to get past Mattek-Sands, who shared two Grand Slam doubles titles this year.

"Knowing that she's capable of having big wins kind of relaxes me because I know she's going to come out and I know what to expect," Williams said.

"She's going to give 300 percent. She's a huge fighter. She has a great game.

"I have to start out strong if I want to stay in the tournament. If not, I can go on vacation."

Williams must also calm the nerves that overwhelmed her at moments in round two.

"I'm going to get back into the place that I was and I'll be fine again," Williams vowed.

The highest-ranked rival on her side of the draw, Swiss teen 12th seed Belinda Bencic, will face seven-time Grand Slam singles champion Venus Williams in another third-round encounter at Ashe. The winner could face Serena Williams in the quarter-finals.

World number one Djokovic, seeking his third Grand Slam title of the year and his fifth trip in six tries to the US Open final, meets Italian 25th seed Andreas Seppi for a place in the fourth round.

The Serbian star would be seeking a calendar Slam sweep of his own had he not lost the French Open final to Swiss Stan Wawrinka.

Spanish eighth seed Rafael Nadal, a 14-time Grand Slam champion, meets Italian 32nd seed Fabio Fognini for a spot in the last 16.

He and Djokovic are on a collision course for a quarter-final showdown.

Defending champion Maric Cilic, the ninth seed from Croatia, and Spanish seventh seed David Ferrer could book a fourth-round meeting with victories Friday.

Cilic faces Kazakhstan's Mikhail Kukushkin while Ferrer takes on 27th-seeded Frenchman Jeremy Chardy.

Slightly cooler conditions were predicted than the past four days, where sweltering heat and humidity have produced a Grand Slam record 12 men's retirements during matches and two more on the women's side.