MASON, Ohio -- The Williams sisters have seldom spent such a miserable day together.
Venus botched routine shots all the way through a 7-6 (2), 6-4 loss to Italy's Flavia Pennetta on Thursday, the first major upset at the Cincinnati Open. She made 38 unforced errors, repeatedly dumping balls into the net or well beyond the baseline.
"I saw her after the match, and she just said she had made a lot of errors," younger sister Serena said. "I was like, 'Wow.' I didn't think I would do the same thing."
Not the same. Worse.
Playing on the same court a few hours later, Serena topped her sister in confounding mistakes. She had 44 unforced errors during a 7-5, 6-4 loss to Austria's Sybille Bammer, who reached the quarterfinals of a tournament for only the third time this year.
"I never played worse in my life," Serena said. "It was really a bad match."
With the Williams sisters gone, the $2 million Western & Southern Financial Group Women's Open became a stage for Kim Clijsters' comeback. She returned from a two-year layoff to recharge and start a family and won her first two matches rather easily. Clijsters persevered through a tough test on Thursday to reach the quarterfinals.
She showed focus and energy in a 6-4, 4-6, 6-2 win over Russia's Svetlana Kuznetsova during the midday heat. The 26-year-old Clijsters swept all four points in the final game and then pumped her fist in celebration.
"My mindset was really good," she said. "I feel really good after this match. It's not that I feel tired or drained or anything, just a few little aches and pains from getting back into playing matches."
The former No. 1-ranked player had to find another way to win points when her serve deserted her early in the match. She made only 39 percent of her first serves in the opening set but managed to win anyway.
"There are patches where my level is really good, then I have a few dips," she said.
She'll play current No. 1 Dinara Safina in the quarterfinals on Friday. Safina beat Peng Shuai of China 6-3, 6-4, setting up a quarterfinal match that doesn't surprise her.
"You cannot lose your talent," Safina said, referring to Clijsters. "You cannot lose anything. It is there. If you are a great player, it doesn't matter."
It's the first time since May at Madrid that neither of the Williams sisters will be in a quarterfinals. Serena lost in the first round of that tournament, Venus in the second round.
Third-seeded Venus made some of her worst shots at the biggest moments on Thursday. She hit a couple forehands long during the first-set tiebreak and ended the match by sending a forehand well beyond the baseline.
"I wasn't able to get control of my ball today," she said. "After a while, it was obvious to see she was just keeping the ball in play and waiting for me to self-destruct."
When Williams' forehand sailed long to end the match, Pennetta raised both arms in celebration and then put her left hand on her forehead as she approached the net.
"I'm shaking," she said, shortly after shaking Williams' hand.
The 27-year-old Italian doesn't usually get so emotional after a match.
"Very unusual," said Pennetta, who won the L.A. Women's Tennis Championships on Sunday. "I don't know. The emotion was crazy. Coming from Los Angeles, I didn't have a lot of days to rest. I was playing like that -- yesterday, not my best tennis. I was tired. When everything comes together, the emotions go up."
Second-seeded Serena was determined not to make it an 0-2 day for the Williams family. They had a great family moment in July at Wimbledon, where she beat Venus in the finals.
"We don't lose too much in the same day, so usually I'm so pumped," Serena said. "And I was pumped today. I just couldn't get it together."
She struggled against a player who was uncomfortable in her first match on the center court. Bammer is ranked No. 29 in the world and beat Serena in their only head-to-head match in 2007, a three-set victory. This was much different.
"I was nervous today, so I don't know how I really played," Bammer said. "I just tried to come into the rallies and make her play, and this worked."
The longer Serena played, the worse she got.
"I just hope I don't have another day like this for another several years," she said.