Serena Williams, Venus Williams
Serena and Venus Williams of the U.S. stand together with Australian Open tennis tournament ballboys and girls during a promotional event at Melbourne Park, Australia, in this handout image taken Jan. 10, 2017 Fiona Hamilton-Tennis Australia/Handout via Reuters

The good news for Serena and Venus Williams is that one of them will enjoy perhaps the defining achievement of their careers Saturday in the Australian Open final. And, if they do, they will have their sister right there with them to share in the moment. The bad news is that they will have to crush the dreams of the person closest to them in order to achieve it.

It is a remarkable twist of fate. As Serena Williams goes for Grand Slam title No. 23, to move ahead of Steffi Graf for the most ever in the Open era, she will have to square off against her elder sister, for whom victory would be just as, if not more, remarkable.

While Serena Williams’ place in the final is far from a surprise – even as a 35-year-old – Venus Williams’ progress this far is already sure to go down as one of the great tennis stories of 2017. Were she to win it, it will be hard to find a better story in all of sports this year.

She may be just over a year older than her sister, but Venus Williams is not only defying age but also the auto-immune disorder Sjogren’s disease, which has left her having to carefully manage her energy since she was diagnosed in 2011. After her diagnosis, she slipped outside the world’s top 100. At the age of 30, having already won seven Grand Slam singles titles, been to No. 1 in the world and with numerous interests outside the tennis court, nobody would have blamed her if she had called time on her career.

Instead, she has kept battling, believing that she had at least one more big result left. Now, in her first Grand Slam final for seven-and-a-half years, she is within sight of one of the sport’s biggest prizes once again.

“Not at all [did I think that these moments might be behind met],” Venus Williams said after beating fellow American CoCo Vandeweghe in three sets in the semifinals. “Not at all. Even the matches I'm not winning, I'm still in control, normally, of every match that I have the opportunity. It's on my racquet, always putting myself in position to be where I need to be.

“Clearly these matches are challenging, physically, mentally, all of that. It's a challenge. But I'm up for the challenge. Also, if I'm here, that's why I'm here. I'm not just here to hang out halfway around the world. This is a long way to come for a hangout session.”

For Venus Williams, the cross she has long had to bear is that her career achievements would read far greater if not for her younger sister. While coming out on top twice, Venus Williams has lost six Grand Slam finals to her sister, including the last one she played in at the 2009 Wimbledon.

And Venus Williams has come out on top just once in the pair’s last eight meetings, giving her sister an overall 16-11 edge. But the younger Williams has not been infallible in major finals of late. Indeed, she lost two last year, including at the Australian Open to Angelique Kerber.

Serena Williams has, though, been faultless on her route through to the final, not dropping a single set, even if the highest seed she has faced was British ninth seed Johanna Konta in the quarterfinals. Now, because of her opponent in the final, she claims she cannot lose.

“It definitely makes it uncomfortable,” she said after beating Mirjana Lucic-Baroni 6-2 6-1 in the semifinals Thursday. “But after everything that Venus has been through with her illness and stuff, I just can't help but feel like it's a win-win situation for me. I was there for the whole time. We lived together. I know what she went through.

“It's the one time that I really genuinely feel like no matter what happens, I can't lose, she can't lose. It's going to be a great situation.”

Prediction: It would be a truly incredible story were Venus Williams to pull out the victory on Rod Laver Arena Saturday. And she is playing well enough that, if her opponent is below her best, the 36-year-old could very well come out on top. Yet both history and current form favors Serena Williams to get the job done.

Serena Williams in straight sets

Match time: 3:30 a.m. EST
TV Channel: ESPN
Live Stream: Watch ESPN