Belinda Bencic upset an ailing Iga Swiatek 3-6 6-0 6-3 to give Switzerland a 1-0 lead before Hurkacz levelled the tie at 1-1 with a 6-3 3-6 6-3 win over retiring veteran Stan Wawrinka under a closed roof at Ken Rosewall Arena.
Swiatek and Hurkacz were slated to back up against Bencic and Wawrinka for the make-or-break mixed rubber, but the respective team captains were expected to tinker with their line-ups.
Katarzyna Kawa and Jan Zielinski have been undefeated for the Poles, while Jakub Paul partnered Bencic to a decisive victory in Switzerland's epic semi-final triumph over Belgium on Saturday night.
Whatever transpires though, the final could well be overshadowed by Swiatek's fitness concerns.
In a worrying development just a week out from the Australian Open, the world No.2 left the court for treatment after suffering a rare bagel in her loss to Bencic in Sunday night's opening match.
Swiatek was in state of complete despair by the end, tossing her racquet across the court and bursting into tears following her second straight defeat at the event.
Swiatek also endured a straight-sets loss to world No.4 Coco Gauff on Saturday night.
Bencic, meanwhile, extended her perfect record this Cup campaign to five singles wins and four doubles successes in piloting the 16th-seeded Swiss outfit to the brink of unlikely title glory at the $17 million mixed showpiece.
Six-time grand slam champion Swiatek was also seen crying at the first changeover during her victory over Australian Maya Joint on Friday night.
It remains unclear what Swiatek's issue or injury is but her fitness will unquestionably be one of the major talking points in the countdown to the season's first major in Melbourne.
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