The elder Williams has rolled back the years with an inspired run to the semi-finals, where a clash with an American upstart and erstwhile fan awaits

Somewhere around the turn of the century, when a young American named Venus Williams was ruling women’s tennis, an even younger local girl named Colleen, who loved tennis but also played a lot of basketball, chased after her for an autograph at a WTA Tour event in Carlsbad, California.

She was denied.

A tennis lifetime later, little Colleen – known now as CoCo Vandeweghe – has reached the first grand slam semi-final of her career. And when she enters Rod Laver Arena in Melbourne on Thursday afternoon, the woman following right behind her will be a familiar face.

Now 36, Venus Williams is still here. And she’s not going anywhere.

The years in between have been a rollercoaster of triumph and struggle, perseverance and grit for Williams. For Vandeweghe, they were years of growing into a strong, powerful body, of promise slow to bloom and now, at the relatively advanced tennis age of 25, an emphatic arrival on one of the sport’s biggest stages.

“I told her one time at Fed Cup: ‘The first time I asked you for an autograph, I didn’t get one,’” Vandeweghe said on Tuesday after a 6-4, 6-0 quarter-final thrashing of French Open champion Garbiñe Muguruza of Spain, the No7 seed.

“She said: ‘Do you want one now?’”

Vandeweghe’s autograph-seeking days are long past. Before dismantling Muguruza, she posted an equally impressive win over world No1 and defending Australian Open champion Angelique Kerber of Germany.

I told (Venus) one time: ‘The first time I asked you for an autograph I didn’t get one.' She said: ‘You want one now?’ CoCo Vandeweghe

There were 18 Americans in the 128-player women’s singles draw at the start of the first major tournament of the season. They ranged from former UCLA standout Jennifer Brady, a qualifier who reached the fourth round, through solid, unheralded pros like Varvara Lepchenko, Alison Riske and Christina McHale. Notably, No8-ranked Madison Keys and former top-10 player and Australian Open semi-finalist Sloane Stephens are injured and not even here.

The Williams sisters and Vandeweghe could do something no country has managed since the 2002 US Open: put three of its female players in a grand slam’s final four.

Williams now is a sentimental pick to go deep into any draw; every next time could be the last. But her legend and her legacy obscure the fact that she has not been an odds-on favorite to win a major since back in the days when little Colleen was chasing her for a signature.

To reach the semi-final stage at Melbourne Park, which she has done only twice before, is unexpected – especially after she withdrew from a warm-up tournament in Auckland because of injury. “I had a lot of anxiety coming into this event. More than anything, you know, you don’t want to look silly out there, walk out on the court and just not play well because you just aren’t prepared,” Williams said.

Williams has shown no outward sign of injury, no taping or lack of energy or hesitation in her movement. Her level has been top-notch, but she also has benefited from a dream draw: two of her first four opponents were qualifiers, and the highest-ranked of the four was Ying-Ying Duan of China, at No87.

The highest-ranked players in her section, No4 seed Simona Halep of Romania and No8 Svetlana Kuznetsova of Russia, lost before they could face her. No24 Anastasia Pavlyuchenkova, whom she defeated 6-4, 7-6 (3) in Tuesday’s quarter-final, will be the only seed Williams will face unless she reaches the final.

Facebook Twitter Pinterest CoCo Vandeweghe is through to a grand slam semi-final for the first time in her career. Photograph: BPI/REX/Shutterstock

Given Vandeweghe’s current ranking of No35 and the champions standing in her way in the draw, she may have been an even bigger long shot.

The two have met just once before, on Vandeweghe’s least-favorite surface in Rome last year, when Williams won 6-4, 6-3.

Her accomplishments here cannot be discussed without the name “Williams” impertinently interrupting the conversation. With the win over Kerber, Vandeweghe became the first American woman not named Williams to defeat a No1 since Jennifer Capriati upset Martina Hingis at the 2001 French Open. With the win over Muguruza, she became the first unseeded American woman since Serena Williams here a decade ago to defeat two top-10 players the same year.

Vandeweghe’s on-court swagger and her penchant for turning her Yonex racquets into works of modern art make her as polarizing a figure as Williams is a universally beloved one.

But when it comes to the tour’s elder stateswoman, she exudes nothing but awe.

“It’s a dream to play someone you grew up watching. To play an unbelievable player, future Hall of Famer, Venus, to be on the court with her, I’ve only experienced it one time before. But to do it at this stage of a grand slam is kind of crazy. I mean, I can’t really put it into words,” Vandeweghe said.

Williams’s words at this stage are hardly those of an aging icon hoping for one last shot at glory.

“Should I look across the net and believe the person across the net deserves it more? This mentality is not how champions are made,” she said. “I’d like to be a champion, in particular this year. The mentality I walk on court with is: I deserve this.”

Vandeweghe’s sterling athletic bloodlines – her grandfather and uncle were NBA stars and her mother Tauna was an Olympic swimmer – are in stark contrast to those of Williams, whose sporting genius was born of rather unremarkable athletic stock.

But the two come from a similar tennis mold. Both are tall, with big powerful groundstrokes and two of the best serves in the women’s game.

The brand of so-called “big babe tennis” they’ll produce Thursday also is a bit of a throwback, a homage to the years when between the Williams sisters, Lindsay Davenport, Capriati and Monica Seles, there was no quarter given.

As Vandeweghe, poised to crack the top 15 if she wins on Thursday in Melbourne, joins the Williamses and Keys in the tour’s uppermost echelon, it seems another great era of American power is dawning.