Badosa conquered Belarusian star Sabalenka en route to the Western & Southern Open quarter-finals in August.
The Indian Wells champion repeated the feat again on Friday (AEDT), blitzing the No.1 seed in her WTA Finals opener in Mexico.
No.7 seed Badosa, from Spain, played lights-out tennis in Guadalajara, where she powered past Sabalenka after a tricky start to the opening set.
Badosa, who is a French Open quarter-finalist, found herself down 4-2 before reeling off four consecutive games to clinch the first set at the year-ending championship.
In the Group Chichen Itza match-up, Badosa continued where she left off in the second half, winning 10 straight games in total in an irresistible performance to hand Sabalenka a bagel.