NEW YORK -- When it comes to tennis, Serena Williams has been there and done that. She has won 11 Grand Slam singles titles, two Olympic gold medals and more than $25 million in prize money.
After luring Flavia Pennetta to net with a drop shot on Tuesday evening, she fired a forehand winner down the line, completing the best point of the match -- and, indeed, the match itself. And then Serena went into hysterics, shrieking and pumping her fists in Arthur Ashe Stadium with the sound and fury of, well, something greater than having achieved merely another Grand Slam semifinals berth.
Why? Because, tennis fans, Serena Williams wants it.
While most of the rest of the women's field has checked out of the U.S. Open hotel and withdrawn to comfortable homes in Eastern Europe -- there were only two seeded players, No. 9 Caroline Wozniacki and No. 2 Williams, in the final six -- Serena wants to win another Open.
She holds three of the four major trophies and, based on the deep lines of intensity creasing her features, seems destined to make it four of five.
"I'm not aware of it, but I see it after in photos," Serena said. "I'm pretty horrified sometimes. I think, 'Oh, my god. Who is that?'"
Who can stop her?
"I don't think anyone can," said ESPN analyst Pam Shriver.
"She goes about her business, fulfills her obligations, then turns it up at the Slams. That's been her pattern. Until it costs her a major or two, I don't think she's going to change. How she's been playing, along with the way the rest of the field has done, she's a huge favorite," Shriver said.
She has seen that withering look, the one that unnerves most of Serena's opponents.
"She has that face," Clijsters observed, "where she's like, 'OK, I'm here to do business.'"
This is the fearsome face that Pennetta ran into in the quarterfinals. The top-10 Italian had saved six match points in her previous match with Vera Zvonareva. She had won 20 of 22 matches down the sizzling summer stretch, but Serena chilled her out in an instant. The match was humming along, on serve at 4-5, when Serena won the first three points on Pennetta's serve. A nervous forehand sailed long and Serena had landed the first set.
The final was 6-4, 6-3.
"When you play with this player," Pennetta said, "you cannot make a mistake."
Serena has blown through her five matches without losing a set; she's the only man or woman to come through so far unscathed and has lost a total of only 24 games. She has won 23 of her 24 Grand Slam singles matches this season.
"I'm really excited to have that fire," Serena said. "It's cool that I have a chance to get involved and to be able to lift my game when I need it in a really intense moment.
"I never give up in anything I do, whether I'm playing tennis or whether I'm writing or -- well, I do give up if I'm running, because I don't like to run," she said.
Clijsters, who remains one of the sweetest, most considerate players in the game, insisted that even Serena sometimes gives you an opening. Even though she has lost seven of her eight matches with Serena, albeit from 1999 to 2003.
"Every player always has a moment in a match where, whether it's either one or two games, where they just kind of lose that aggressiveness little bit or just lose focus," Clijsters said hopefully. "It's up to the other player to kind of feel that and step it up at that time.
"Something that I'm going to be really focused on is obviously play aggressive tennis and try to dominate a lot of points. I think the one who keeps the unforced errors down I think is going to get through here," she said.
Only two women have beaten both Williams sisters in the same Grand Slam event: Martina Hingis (2001 Australian Open) and Justine Henin (2007 U.S. Open). Clijsters, who beat Venus in the fourth round, would like to be the third.
Serena watched that match between Clijsters and her older sister.
"I just saw how well she moved," Serena said. "Seems like she's even faster than she was before. I was thinking maybe I should have a baby, and then I'll come back faster.
"That was my observation, so I'm thinking about it," she said.
Greg Garber is a senior writer for ESPN.com.