Venus Williams rallied from the disappointment of losing a tight first set to blast her way past Caroline Garcia 6-7(3) 6-2 6-3 and set up a WTA Finals title showdown against Caroline Wozniacki on Saturday.
The evergreen American has enjoyed a brilliant campaign, reaching two grand slam finals in 2017, and the 37-year-old American was able to call on all her experience to find a way to stifle her upset-minded opponent in an engrossing encounter.
In the first semi-final, Denmark's Wozniacki stood her ground in the face of some incredible early pressure before pinning down Karolina Pliskova with a 7-6(9) 6-3 victory that ensured Simona Halep will end the year as world number one.
Williams and Garcia took the court in a battle between two players possessing huge forehands and a tendency to attack their opponent's second serve, the contest starting out as slow burner that lacked fluency after they traded early breaks.
Williams appeared troubled by a hip injury and was trying to keep the points short while Garcia became tentative every time she had a chance to break free, especially when she fashioned her first set point that came and went at 5-4.
Garcia was rewarded for being more positive in the tiebreak as Williams' serve wavered and the Frenchwoman wrapped up the opener on her second set point when her opponent sent another groundstroke wide and long.
The American increased her intensity in the second set and took advantage of Garcia's passivity to storm 4-1 clear, with Williams breaking for a second time in the eighth game against a weary-looking opponent to level up the contest.
Garcia had won nine of her last 10 three-set matches but was struggling to grab any sort of foothold in Williams' service games and the American shifted up a gear to grab the only break she needed in the eighth game and served it out for the win.
"Garcia competed so well in the whole tournament," Williams said of an opponent who won back-to-back titles in China to sneak into the event as the last qualifier.
"Every time I thought I had her, she would play amazing shots... but it's never over until the fat lady sings and I'm not fat," joked Williams, who won the tournament in 2008.