MASON, Ohio -- Kim Clijsters' comeback ran into a No. 1 problem.
Playing her first tournament in more than two years, the Belgian couldn't keep up with the world's top-ranked player on Friday. Dinara Safina repeatedly broke her serve during a 6-2, 7-5 victory to reach the semifinals of the Cincinnati Open and finish Clijsters' uplifting week back on the court.
With both Williams sisters gone, Clijsters' return became the talk of the $2 million Western & Southern Financial Group Women's Open. The former No. 1-ranked player took a break in 2007, married basketball player Brian Lynch, gave birth to daughter Jada, then set about returning to the game at a top level.
While she was away, Clijsters watched one player improve more than any other: Safina.
"I really felt today that Dinara played some of her best tennis that I've seen," said Clijsters, who won six of their seven previous matches. "I think by far that's the best she's ever played against me."
No mother has knocked off a No. 1-ranked player since Evonne Goolagong Cawley beat Chris Evert in the finals of the Virginia Slims of Boston in 1978. Thirty-one years later, Clijsters got a good start at it, pushing the pace and getting a service break for a 2-0 lead.
It unraveled fast.
Safina used her powerful forehand to her advantage, hitting shots that eluded Clijsters' reach. She dominated the rest of the set, running off 24 of the last 31 points. For the first time all week, Clijsters looked like a player who had been off the tour for two years.
"I know exactly what to expect from her," Safina said. "For me, she's one of the best players. I thought I was very aggressive today and didn't let her dictate too much."
Clijsters started the second set by pushing the pace and getting another quick break to pull ahead 2-0.
Same beginning, similar ending.
Safina broke her serve three times in a row, the last on Clijsters' double fault to take a 6-5 lead. When Safina served it out, Clijsters calmly removed her black wristband and visor, walked to the net, shook her hand, packed quickly and headed out.
Disappointing, but not discouraging. Clijsters played well overall in her four matches during the week, surpassing her expectations in some ways.
"Obviously so far, it's working," she said. "I had really good results, and feel my level here has risen."
So much that she was already aching for another shot at No. 1.
"I kind of feel like I want to go out there and do it all over again," Clijsters said.
Fourth-seeded Elena Dementieva also advanced with a 6-2, 6-1 win over Caroline Wozniacki. It's the fifth semifinal this year for the Russian, who lost to Serena Williams at the Australian Open and at Wimbledon in semifinal.
It won't happen again this week. Serena and Venus Williams were bounced from the tournament on Thursday.
Dementieva will play Serbia's Jelena Jankovic, who beat Sybille Bammer 6-0, 6-3 in only 62 minutes. Bammer knocked Serena Williams out of the tournament on Thursday, but managed to win only 10 points while getting swept in her opening set against the fifth-seeded Jankovic.
A day after she upset Venus Williams, Italy's Flavia Pennetta reached the semifinals with a 6-3, 6-3 victory over Daniela Hantuchova of Slovakia. The win set up a semifinal against Safina and assured Pennetta of becoming the first Italian woman to move into the Top 10. Two Italian men, Adriano Panatta and Corrado Barazzutti, were ranked in the Top 10 in the 1970s.
"It means a lot," said Pennetta, currently ranked No. 12. "Everyone expected something like that from the beginning of the year, so everyone talks about it all the time. You know, it's a dream come true for me. I always hoped to be one of the best players in the world, and now I'm there. So it's crazy."