Serena on elder Aussie Open semifinalists: '30s is the new 10'

Maybe it's true you can't teach an old dog new tricks, but when you get this much mileage out of the old tricks, what difference does it make?

There is an unprecedented wealth of experience in the Australian Open semifinals, with six of eight participants over the age of 30, and half of them having celebrated at least their 34th birthdays.

Two such players will meet in the second women's semi on Thursday's docket, and 35-year-old Serena Williams - who has defied the aging curve like none before her - thinks she and her 34-year-old opponent, Mirjana Lucic-Baroni, are playing like players more than two decades younger.

"Thirties is the new 10," Williams said in her on-court interview after beating Jo Konta in the quarters.

She and Lucic-Baroni will be playing for the third time in their careers, but the first time since 1998, when both were in fact much closer to 10 than they are to their present mid-thirties selves.

"I'm so proud of Mirjana. She's been playing so well," Serena said. "We played well over a decade ago. Oh my god, almost two decades ago. It's so good to see her back out, and to see her in the semifinal is really just so inspiring for me. I'm so happy for her, and no matter what happens, someone 34 or older will be in the final, and that's just really awesome."