Starting seventh, Shiffrin watched as Velez Zuzulova had her skis go out from under her around a turn. Shiffrin avoided trouble on a demanding Red Dog course in which there were more than a dozen racers who didn't finish the slalom.
"I thought, 'OK, so now I have the globe. I still want to have a good race today,'" said Shiffrin, who held a 145-point lead over Velez Zuzulova heading into Saturday's race. "I was sort of struggling in my mind with how much effort I need to put into it, how much risk I needed to take.
"I don't have a ton of energy right now. I don't have enough to make a good recovery if I happen to make a mistake. I took a little bit off the gas pedal in order to find a rhythm and it took a little bit longer than I would've liked. But it was as solid run and I didn't make any big mistakes and so now I have a shot."
Shiffrin rose to prominence in the slalom, capturing gold at the 2014 Sochi Olympics and three straight titles at the world championships.
Her fourth crystal globe in the discipline ties her with Austrian skier Marlies Schild. Vreni Schneider of Switzerland has the most slalom titles among women with six.
What's more, Shiffrin's closing in on joining Phil Mahre, Tamara McKinney, Bode Miller and Lindsey Vonn as the only Americans to win the overall crown. Ilka Stuhec of Slovenia is 278 points behind Shiffrin and didn't race Saturday.
After this weekend, there are four races remaining at the World Cup Finals in Aspen, Colorado.