NEW YORK -- Kim Clijsters pulled off another upset that didn't really look like one. Now, she's only two wins from a U.S. Open title hardly anyone could have seen coming.
The mother of 18-month-old Jada, Clijsters dismantled 18th-seeded Li Na, 6-2, 6-4 in the quarterfinals Tuesday, punishing China's top tennis star with deep, stinging groundstrokes that were part of a game that looked about like it did when Clijsters retired two years ago.
Or maybe better.
The 26-year-old Belgian is back at the U.S. Open for the first time since 2005, when she won the tournament, and now has a winning streak of 12 matches at Flushing Meadows. Her next match will be against No. 2 Serena Williams, who beat No. 10 Flavia Pennetta 6-4, 6-3 to improve to 23-1 in Grand Slam singles matches this season.
Looking ahead to facing Clijsters, Williams said: "She's such a great person and I, like, only wish the best for her. But not in the next match."
Williams has won seven of eight career meetings with Clijsters. The first time they met was in the third round of the 1999 U.S. Open, which Williams won en route to her first Grand Slam singles crown.
"She plays tough. She plays hard," Williams said. "Now it's like a totally different level, because she has absolutely nothing to lose. I think that's when you can play your ultimate best tennis."
Clijsters has already beaten No. 3 Venus Williams and two other seeded players, and nothing seems like too big a stretch at this point.
"I'm glad I got through it again, stayed focused on my game," Clijsters said. "I wanted to be aggressive and I think that's what helped winning those important points today."
The few important points there were in this one came midway through the second set, after Clijsters had lost a break to turn a 3-1 lead into a 4-4 tie. Li responded with four unforced errors to give away the ninth game and the match was over a few minutes later.
Clijsters became the first unseeded player to make the U.S. Open semifinals since Elena Dementieva in 2000. Clijsters was unranked because she hadn't played enough tournaments in her comeback to get on the board, but she'll be in the low-50s or better when the next rankings come out.
As efficient as she has been -- moving better now than she did when she was constantly battling injuries toward the end of her last stint -- her run through this tournament might also be seen as a statement about the state of women's tennis.
Serena Williams is the only top-five seed left. Three of the players on the opposite side of the draw -- the "Melanie Oudin side" -- are ranked 50 or higher, joined by No. 9 Caroline Wozniacki. All are playing in their first major quarterfinals.
"I saw her when she came back in her first tournament," Li said, referring to Clijsters. "I knew she was at a high level. She's much stronger than other girls, so I knew, if she was going to come back, it must be a strong comeback."
Williams has won three of the past four major championships. She is seeking her fourth U.S. Open title and 12th Grand Slam overall.
With her older sister Venus sitting in the stands, Williams piled up a 21-9 edge in winners against Pennetta, who was trying to be the first Italian woman to reach a Grand Slam semifinal.
"She was playing really well," said Pennetta. "She was really aggressive. The ball was very heavy for me tonight. She was playing really great, really aggressive. When you play with this player, you cannot make mistakes. Today I make a few mistakes on important points.
"I give everything on the court tonight," Pennetta said. "I was like running and fighting until the end. It's the only way to win against this kind of player. I was there but tonight was not my night."
Information from The Associated Press and Reuters was used in this report.