Keys served for the match in the second set but incoming world number one Sabalenka overhauled the 2017 runner-up to win 0-6, 7-6 (7/1), 7-6 (10/5) to reach her second Grand Slam final.
“I’m really proud of myself that I was able to turn around this game and get this win, because it was just incredible,” said Sabalenka.
“I was just, like, ‘Come on, keep trying, keep pushing, like, I don’t know, do something extra. Just try to turn around this match.’”
“It really means a lot to be in the final of the US Open for the first time,” she added.
Sabalenka rode an emotional rollercoaster, angrily remonstrating with her coaching team at times, before being able to sheepishly laugh off celebrating prematurely in the decisive tie-break. “I thought that we play tie-break up till seven. I was just all over the place,” she said.
The Australian Open champion will bid for her second Grand Slam title on Saturday against the 19-year-old Gauff. The American holds a 3-2 edge but this will be their first meeting at a major.
“She’s an unbelievable player,” said Sabalenka. “The crowd will be supporting her a lot. I will do everything I can. I’ll be fighting for every point and I will do my best.”