Melbourne: Only three women can now prevent Serena Williams from clinching a 23rd grand slam title on Saturday, her sister Venus, a younger compatriot and a 34-year-old Croatian she last played nearly two decades ago.
The quartet take to Rod Laver Arena on Thursday with Serena playing Mirjana Lucic-Baroni and Venus facing Coco Vandeweghe at the business end of an Australian Open where upsets have been a daily occurrence.
The seedings have not proved much of a guide in the women's draw this year, with world number two Serena the sole survivor of the top 12 at the start the tournament.
The head-to-head will not provide much help either when assessing Serena's matchup against Lucic-Baroni, given their last meeting came in 1998 at Wimbledon when they were both 16. "It was on Centre Court. That's all I remember. I remember winning. I was so excited because I was so young. She obviously was super young, too. That's all," Serena said on Wednesday after beating Johanna Konta in the quarter-finals. "We have totally different games now, the both of us. We both have gone through a lot. We both have survived, and here we are, which I think is a really remarkable story."
As six-times Melbourne Park champion, Serena will be clear favourite, of course, more so because she has reached her 34th grand slam semi-final without losing a set.
Lucic-Baroni's path to the last four has been more of a battle, as befits a woman who has overcome huge adversity to get back to the top of the game after years in the wilderness.
While Serena missed the back end last season with a shoulder problem, Lucic-Baroni has more immediate concerns about an injury to her left leg.
"I'm going to be just fine," said the world number 79. "I'm going to recover, do some therapy, and I'll be fine. I'll just put some extra tapes on and hopefully it will hold me together. I'll fight hard. I'll be okay."
The first semi-final is an all-American affair pitching Venus, the oldest woman in the draw, against 25-year-old surprise package Vandeweghe.
Venus does not have an Australian Open crown in her collection of seven grand slam titles and has reached the final just once, losing to Serena in 2003.
Vandeweghe has got to the last four of a grand slam for the first time here by blowing opponents off the court with her booming serve and big winners.
Venus might be hoping that the occasion gets the better of the world number 35 but promised nevertheless that the power tennis would not be coming from just one side of the net.
"Power is her game, her strength. She's putting the ball in with it, it's awesome to see really," Venus said.
"(But) I play a power game as well. I've been fortunate enough to play good defense and have good movement around the court. Hopefully this will be a plus for me."
Vandeweghe was seven years old when Venus first played at the Australian Open and said it remarkable to think she was about to face a player she once asked for an autograph.
"It's a dream to play someone you grew up watching," she said. "To play an unbelievable player, future Hall of Famer, Venus, to be on the court with her but to do it at this stage of a grand slam is kind of crazy."