France's Amelie Mauresmo reclaimed the world number one ranking without hitting a ball.
Mauresmo, who topped the rankings for the first time 18 months ago, deposed Belgian Kim Clijsters despite both players skipping last week's event in Indian Wells, California.
The rankings are determined by results over the preceding 52 weeks and on Monday U.S. Open champion Clijsters lost more points from her tally than Mauresmo because she won last year's Indian Wells event.
Mauresmo, who won her maiden Grand Slam title at the Australian Open in January, has 3,511 points to Clijsters's 3,290. Indian Wells winner Maria Sharapova of Russia moved up one place to fourth on 2,753, one place behind Belgian Justine Henin-Hardenne (2,944).
Mauresmo and Clijsters are expected to play in this week's WTA event in Miami, where Clijsters is also defending champion.