NEW YORK - World number one Serena Williams, seeking her 17th Grand Slam title, leads a charge of 31-year-olds into Friday's US Open semi-finals, all of them hoping to become the event's oldest women's champion.
Defending champion Williams faces Chinese fifth seed Li Na while Italy's 83rd-ranked Flavia Pennetta will meet second seed Victoria azarenka of Belarus at Arthur Ashe Stadium to determine the finalists for Sunday's title showdown.
Williams, Li and Pennetta are all 31 and would surpass the current age mark of Australian Margaret Court, who was 55 days beyond her 31st birthday when she captured the 1973 crown.
Azarenka, the self-proclaimed "baby" of the group at 24, has won the past two Australian Open titles but lost to Williams in last year's US Open final.
Williams, the reigning French Open champion, is 8-1 all-time against Li and has dropped only 13 games in five matches without losing a set on the New York hardcourts.
Li, the 2011 French Open champion, has played Williams tough, forcing a tie-breaker or 7-5 set in every defeat, including their most recent match, a 7-5, 7-5 triumph for the American in a semi-final last month at Cincinnati.
"She's a great challenge," Williams said. "She moves really well. She does everything well.
"She has been playing really close. Who knows? Maybe the next time we play she might want to go from close to a win, so I have to be ready for that."
Li knows dethroning a four-time US Open champion will be a heavy challenge, but she has been aggressive and formidable herself in the Flushing Meadows fortnight.
"It's a tough, tough opponent," Li said. "But it's a good challenge to play against her, because I think we always have a tough match, even in Cincy.
"Yeah, I still have a chance."
So does Pennetta, the fourth-lowest-ranked US Open women's semi-finalist after unranked 2009 winner Kim Clijsters, unranked 1979 semi-finalist Billie Jean King and 92nd-ranked German Angelique Kerber, a 2011 semi-finalist.
"I have nothing to lose," said Pennetta who has split her two career matches with Azarenka.
The Italian is a Grand Slam semi-final debutante who has yet to drop a set after missing last year's US Open with a right wrist injury that is only now healing enough to let her play her best.
"To see her go through the injuries and coming up with the results she has right now, it's really amazing," Azarenka said. "The ranking doesn't really matter. It's about the moment. Right now she's playing terrific tennis.
"She has a great touch, great variety. She can create power, create spin. I'm really looking forward to that match It's a big challenge."
Five 30-and-over women reached the last eight, matching the 1977 Australian Open for most in any Slam quarter-finals. Had Daniela Hantuchova upset Azarenka in the quarter-finals, it would have been the first 30-and-over Slam last four.
"I feel so good, so healthy, every time I walk on the court," Williams said. "I'm actually serving harder than I ever have in my career. The racquets are stronger and I'm more fit. I have been able to keep up with the times."
And unlike Wimbledon winner Marion Bartoli of France, who retired last month, these women simply refuse to go away.
"We just keep playing," Pennetta said. "Before the career of the woman was shorter. They retired early. But I think it's because we just keep playing."
Azarenka sees how her older rivals have been able to hang on longer.
"It's just showing that our sport is taking physical ability on another level," Azarenka said. "You see everybody taking care of their bodies much more, really paying attention to nutrition, fitness. Everybody is working out."