The elder of the sport's most famous sisters yesterday gave the world another reminder of just how capable she remains of rewriting history - and she could yet do so again today, when she plays "good friend" Caroline Wozniacki in the final of the BNP Paribas WTA Finals Singapore presented by SC Global.
"She played so well".
The American hit back to take the next two sets, recovering from 0-40 down to serve out the match and make her first appearance in the final for eight years.
After the match, the Dane said: 'It feels unbelievable, I can't believe I'm here as the victor. "So I will see what she's doing, see what's working", Williams added.
Simona Halep has only just been crowned as year-end World No.1, but she says she knows her 2018 will be complicated by the return of Serena Williams and the first full year back for Maria Sharapova. You can still work as much as you want.
The beauty of the round robin format is that if you fall in the opening round, as Williams did, you have two more chances to keep your title hopes alive.
Caroline Garcia has made a habit out of winning from hard positions and the Frenchwoman needed to call on her ability to turn around a tough situation once more on Friday to ride her momentum into the last four of the WTA Finals.
Caroline Wozniacki twice finished the year No. 1 without winning a Slam in 2010 and 2011.
Venus Williams rallied at the WTA Finals to beat Caroline Garcia of France 6-7 (3), 6-2, 6-3 Saturday and become the oldest women's finalist at the year-end tournament.
The American's joy was short-lived, though, as Wozniacki completed a third consecutive break to take the first set after 41 minutes of intense action. "I knew she was stepping it up, she had nothing to lose at that point, and she really went for it. Things were going in for her", Wozniacki told reporters.
"I think it's been an wonderful journey and fantastic career that I can be proud of", the 37-year-old Hingis said. I have to gauge how it goes and try to figure out the solution.
"I started thinking I should have lost this set already, so actually this is just a bonus". Martina Navratilova held the previous record, she was 36 when she lost to Monica Seles in the 1992 title clash.
"I felt like it was a little bit of an uphill battle, to be honest".
They traded breaks in games 2 and 3 and the American had to save 4 more break points by the end of the set, including a set point in the 10th game. "So I had a lot of talks with myself at that point". I will not be the aggressive player on court.
"I have played against great players this week, and it's going to be another great fight tomorrow".
Halep is coached by Australian Darren Cahill and she said there will be no changes to her coaching staff into next season.