Muchova had defeated Sabalenka, of Belarus, in their past three meetings. But in Brisbane, Sabalenka was in control, staving off four break points and breaking Muchova - the No. 11 seed - once in each set to win.
In the other semi-final, No. 16 seed Marta Kostyuk of Ukraine pulled off her third upset of the week, crushing No. 4 seed Jessica Pegula 6-0, 6-3 in 56 minutes. On the week, Kostyuk has defeated three top 10 players - Pegula, Mirra Andreeva and Amanda Anisimova - and now will face a fourth in world No. 1 Sabalenka.
She is winless in four matches against Sabalenka.
ASB Classic
China's Xinyu Wang, the No. 7 seed, upset No. 4 seed Alexandra Eala to reach the finals in Auckland. New Zealand.
To advance, Wang had to come from a set down and save a match point in the second set of a match that lasted just under three hours. Wang started with the contest on her side, taking a 5-1 lead in the opening set only to have Eala, a Filipino, win six straight games to snatch the set.
In the final, Wang will meet No. 1 seed Elina Svitolina of Ukraine, who topped No. 3 Iva Jovic 7-6 (5), 6-2 in 94 minutes. Svitolina rebounded after Jovic took a 3-0 lead in the first set, sending that set to a tiebreak and then winning six of the final seven games in the second for the victory.