NEW YORK -- What started out as a breeze turned into something much more difficult for Serena Williams on Saturday.
Williams won her third-round match, 6-1, 7-6 (5) over fourth-seeded Victoria Azarenka, but not before losing her first four match points and getting pushed to the limit in the second set by the Belarussian, who suddenly found her footing in Arthur Ashe Stadium.
On the fourth of those match points, Azarenka ran Williams off the court and Williams slid and did the splits in an unsuccessful attempt at a passing shot, a move that prompted John McEnroe, calling the match on TV, to say, "If I did that, I'd be out for a year. Life."
Williams got back up but Azarenka broke serve to tie the second set at 5. They went to a tiebreaker and nobody led by more than two points in a back-and-forth thriller that included six winners and an ace -- an electric conclusion to a match that started out as a snoozer.
Williams won the first set in 28 minutes and looked every bit the favorite in a tournament that has lost its defending champion, Kim Clijsters, the Wimbledon and French Open champs, Petra Kvitova and Li Na, three-time major champion Maria Sharapova, along with Williams' sister, Venus.
Because Serena hasn't played much this year, she came in seeded 28th. That set her up for an early match with Azarenka -- a match that, quality wise, might have been more appropriate for the second weekend at Flushing Meadows instead of the first.
Williams hit 39 winners and had only 24 unforced errors and Azarenka went for a lot, too -- making 18 winners and 22 unforced errors.
Williams' next match will be against the winner of a third-round meeting between American Sloane Stephens and 16th-seeded Ana Ivanovic.
Earlier, No. 3 Roger Federer defeated 27th-seeded Marin Cilic 6-3, 4-6, 6-4, 6-2 to make it to the round of 16 for the 30th straight time in a Grand Slam tournament.
Federer needs an Open title to extend his streak to nine straight years with a major championship. He fought off the range of his 6-foot-6 opponent and dealt with an unpredictable wind on the show court to win his 225th match at a major, second best behind Jimmy Connors.
Earlier in the stadium, top-seeded Caroline Wozniacki rolled through her third straight match, avoiding the upset bug that has turned big sections of the women's bracket into a free-for-all.
Wozniacki, the Open runner-up in 2009, defeated American Vania King 6-2, 6-4 and has lost a total of 12 games over her first three matches. Like Federer, it took her time to figure out the breezes on a warm, windy day in New York
In early men's play, No. 20 Janko Tipsarevic was leading No. 9 Tomas Berdych 6-4, 5-0 when Berdych quit with a shoulder injury -- something that started bothering him last month at a tuneup in Cincinnati.
Tipsarevic's opponent in the fourth round will be 2003 French Open champion and U.S. Open runner-up Juan Carlos Ferrero, who was leading 6-1, 4-3 when No. 31 Marcel Granollers retired with an abdominal muscle injury.
The Spaniard was the 14th player to quit in the middle of a match over the first week, the most for any Grand Slam tournament in the Open era. The previous record was 12 at Wimbledon in 2008.