Safina has yet to win a Grand Slam title
Defending champion Dinara Safina made a shock exit from the Madrid Open as she slumped to a 7-6 7-6 defeat by Czech qualifier Klara Zakopalova on Monday.
In a match littered with 14 breaks of serve - seven for each player - the Czech, who is the world number 88, won the tie-breaks 7-1 and 7-3.
Safina's defeat follows the first-round exits of big stars Justine Henin, Maria Sharapova and Svetlana Kuznetsova.
But Serena Williams beat Vera Dushevina 6-7 7-6 7-6 to reach round three.
Williams came back from a set down and needed two tie-breaks to see off the Russian, who is ranked 43 in the world.
The world number one looked to be on her way out after facing match point at 5-6 in the second set.
But Williams clawed her way back to win, despite receiving lengthy treatment for thigh and back problems.
She was forced to leave the court when 3-2 up in the third set, before returning with strapping on her right thigh.
The American is playing her way back into form having been out of action for three months with a knee injury since claiming her 12th Grand Slam title at January's Australian Open.
Williams admitted to being rusty after her return to the court in last week's Italian Open in Rome, where she went out in the semi-finals to Jelena Jankovic.
"I feel really proud because I definitely wasn't playing my best tennis. I was far off playing well," Williams said.
Last year's defeated finalist Caroline Wozniacki, the world number two, looked to have recovered from a recent ankle injury and brushed aside another Czech qualifier Petra Kvitova 6-4 6-2.
In other first round action, eighth-seeded Australian Samantha Stosur edged past Argentine Gisela Dulko 7-6 7-5 and 16th seed Nadia Petrova beat Russian compatriot Elena Vesnina 4-6 6-2 6-3.
In the men's first round, qualifier Oleksandr Dolgopolov Jr of Ukraine beat Italy's Andrea Seppi 6-3 6-4 to set up a clash with Rafael Nadal.
Austria's Jurgen Melzer beat South African qualifier Kevin Anderson 6-2 2-6 6-4 to set up a meeting with either David Nalbandian or Tomas Berdych while twelfth-seeded Gael Monfils of France beat compatriot Stephane Robert 6-2 7-5.
Meanwhile, Roger Federer insists he will not be overly concerned if he fails to defend his Madrid Masters title this week.
The world number one has a first-round bye in Spain as he continues his preparations ahead of the French Open - the Grand Slam he won for the first time last year.
Federer has struggled so far on clay this season, losing in his opening match in Rome and going down surprisingly in Estoril last Saturday to eventual winner Alberto Montanes.
"It would be great to win here again if I could. I can get confidence on the practice courts," Federer said.
"For me, the Madrid title in 2009 was the key to Paris. Winning the event by beating fellow rivals was very important. But no matter what happens here, I'll be prepared for Paris.
"[Form] is not far away. I'm doing the right things and I'm not worried. I really hope to do well here."