Serena Williams will try to make history against a rising star who wasn't even born when the American won her first US Open final in 1999.
But Serena already knows 19-year-old Bianca Andreescu only too well.
It was Andreescu who comforted Williams in Toronto when Serena had to pull out of their Rogers Cup final match after just four games. Those back spasms just a few weeks ago don't seem to have returned since.
'I told her she was a beast and she would bounce back and she has,' Bianca explained. 'It's a dream come true playing against Serena in the US Open final. It's crazy.'
For her part, Serena can't believe she is still going strong. About to make a record tenth Flushing Meadows final appearance, some twenty years after she won her first US Open title as a raw 17-year-old.
'At 17 I thought for sure I'd be retired at 28 or 29 and living my life. So I would have thought this was a sick joke,' admitted Williams.
For a fourth time, Serena will play a major final while bidding to equal Margaret Court's 24 Slams. There have been two missed opportunities in Wimbledon finals and her controversial US Open final defeat to Naomi Osaka last year.
Serena won't want to give the powerful Andreescu as many early chances as she gave Elina Svitolina in their semi-final. She offered up three break points in the very first game but somehow held.
Svitolina was 40-0 up in the next game but Williams won that too. Ater more than nine minutes of intense struggle, Serena had her first break.
The Ukrainian had three more break points of her own at 1-3. Her title bid was effectively over when she squandered those too.
'I just wish I could have taken those opportunities,' Svitolina reflected ruefully later.
Despite a highly impressive opening service game in the second set, Svitolina just dissolved after that. Serena came up with so many acute cross-court angles in this semi-final, her younger opponent simply couldn't cope.
It made you wonder what Britain's Jo Konta could have done if she had been able to turn the screw and maintain the pressure on big points after playing her way into promising positions.
But you have to say that Williams and Andreescu are at a level of their own this time around in New York.
They are the pair with the mental strength to hold their nerve and bounce back when the going gets tough. That's what should make it a great final.
Andreescu never quit when Belinda Bencic was 5-2 up and serving for the second set in their semi-final. The Canadian dug deep, blasted away and won through 7-6 (7-3), 7-5.
So who will win the US Open 2019 title? Andreescu if she settles early and doesn't let the occasion get to her. She has won her last 22 completed matches.
She rested before Flushing Meadows and we said before the tournament she was a dark horse to win the whole thing.
But we also said you could never count Serena out because she is always so dangerous. And after she beat Maria Sharapova in the first round, we underlined that Williams was a serious title contender once more.
If Serena shakes off those recent final nerves and unleashes the inner warrior from the start, she could yet blow Bianca away.
There is no room for self-doubt if Williams is to equal Court's 24 Slams this weekend.
She has to be the ruthless bully from the start. Then she can take her turn to comfort her rival when all is said and done.