Amelie Mauresmo's hopes of ending the year as world number one were dealt a blow when she was thrashed by Nadia Petrova at the WTA Championships.
Petrova is enjoying her best year and has won five titles
Petrova completely dominated, racing to a 6-2 6-2 victory in the opening match of the season finale in Madrid.
Mauresmo was playing for the first time in a month following a shoulder injury.
In Tuesday's other matches, Maria Sharapova beat Elena Dementieva 6-1 6-4 and Justine Henin-Hardenne saw off Martina Hingis 6-2 6-7 (5-7) 6-1.
Fifth seed Petrova broke Mauresmo in the third game and took the set despite Mauresmo successfully challenging to save one set point.
606 DEBATE: Who will win the WTA Championships?
The Russian powered on in set two and earned triple match point, only to drop serve, but Mauresmo was then broken for the fifth time and the match was over in 73 minutes.
"There's nothing to say about that match except it could be worse in the next couple of matches," said Mauresmo.
"It's hard to say anything positive about a match like that. I speak better Spanish than I played today.
I hope it is going to get better as things will only get tougher from here on
"There was no pain in my shoulder tonight - I just feel a little behind the play and I made stupid mistakes.
"Petrova didn't have a great game, she had a good game, a smart game, and that's what's frustrating."
US Open champion Sharapova, who has not lost since August, broke Dementieva immediately and swept through the opening set.
Dementieva fought back in the second, holding in a marathon fourth game and breaking when Sharapova served for the match at 5-3, but her own serve then let her down again.
"I don't think I played my best tennis, the first game at any tournament is never easy," said Sharapova.
"I hope it is going to get better as things will only get tougher from here on."
Dementieva said: "She is playing like a number one now and I don't think anyone else at the moment can play close to her game."
Henin-Hardenne served for the match at 6-2 5-2 against Hingis but let the Swiss back in before regaining control in the final set.
"It was a good game I was playing, I just lost a little bit of my intensity at the end of the second set," said Henin-Hardenne.
"In the third set I started to play down the line again, played technically better, and started to come back to the net."
Yellow Group:(1) Amélie Mauresmo (Fra), (3) Justine Henin-Hardenne (Bel), (5) Nadia Petrova (Rus), (7) Martina Hingis (Swi)
Red Group:(2) Maria Sharapova (Rus), (6) Kim Clijsters (Bel), (4) Svetlana Kuznetsova (Rus), (8) Elena Dementieva (Rus)