Amelie Mauresmo delivered a crushing blow to Kim Clijsters's bid for the number one ranking when she beat the Belgian 6-3, 7-6 at the WTA Championships on Wednesday.
The second-ranked Belgian, who also lost to France's Mary Pierce on Tuesday, will now have to beat Elena Dementieva and hope that Dementieva takes down Mauresmo to have a chance of progressing in the elite round robin competition.
Clijsters needs to go one round better than Lindsay Davenport to seize the year-end number one ranking.
"Of course I'm disappointed," said Clijsters, who has won nine titles this year.
"I would rather have played better and won but there are a lot of other girls who are good players and maybe it's their time to win this time."
Pierce and Davenport scored their second successive victories, putting themselves in prime positions to advance to the semi-finals.
Top-ranked Davenport struggled, but overcame Patty Schynder 6-3, 7-5, while Pierce won her 500th career match, beating Dementieva of Russia 6-2, 6-3.
Clijsters, who has been complaining of jet lag, put in another shaky performance, frequently hitting short and allowing Mauresmo to take the match to her.
Mauresmo served and volleyed her way to an easy first set and appeared to be well on her way to a routine straight sets win in the second set, but was briefly overcome by nerves.
Holding a 5-3 lead and two match points on Clijsters serve, Mauresmo missed a forehand return and then watched Clijsters rip a backhand down the line.
Clijsters held to 5-4 and then broke Mauresmo for the first time in the match when she forced the Frenchwoman into a backhand error.
But the 22-year-old Belgian was never able to find her consistency and in the tiebreak committed a series of unforced errors including an easy forehand on match point.
SHUT DOWN
U.S. Open champion Clijsters, who committed 36 unforced errors to only 26 from Mauresmo, said her body was telling her to shut down for the season.
"My body has had enough," she said. "I remember at the U.S. Open after I won a really tough match against Venus, I was able to bounce right back physically and mentally the next day. Now I don't feel like that."
Neither Davenport nor Schynder was pleased with the way they played in the second set, failing to capitalise on multiple opportunities.
Davenport was broken to love at 4-5 when she double faulted, but the left-handed Swiss lost control of her dangerous forehand and was broken back to 5-5.
After Davenport held to 6-5, Schynder played a poor service game and lost the match when she missed a forehand down the line.
"I felt I was really tiring out there and felt I needed to win in two sets," said Davenport, who leads her round-robin group. "But now I feel like I'm in a good position."
With her quick win over the tired Dementieva, Pierce leads the Black Group.
Pierce saw the ball well all evening and never allowed the Russian to keep her running in long rallies.
The 30-year-old became the third active player after Conchita Martinez and Lindsay Davenport to reach 500 wins.
"That's pretty cool. I'm proud of that," said Pierce.