Swiatek battles past rust to topple Krejcikova in WTA Finals opener
Poland's Swiatek lost in the US Open quarter-finals in September and was leapfrogged in the world rankings by Aryna Sabalenka after opting to skip the WTA Tour's Asian swing due to fatigue.
The Pole, who is looking to reclaim top spot in the Saudi Arabian capital, dropped serve early and was unable to gain a foothold as Wimbledon champion Krejcikova ran away with the first set.
Krejcikova broke twice in the second set after two double faults by an increasingly off colour Swiatek, whose fans at the King Saud University Indoor Arena sensed a big upset and looked to lift the French Open champion.
Swiatek came out swinging from 3-0 down and moved ahead for the first time with a thumping backhand winner, before levelling the match at one set apiece.
She held to love for a 5-0 lead in the decider as Krejcikova struggled with a lower back issue and withstood a late charge to close out victory.
With Sabalenka defeating Zheng Qinwen on Saturday, Swiatek will need to retain the trophy after winning at least two round- robin matches to have any chance of overtaking the Belarusian and finishing as year-end world number one.
Former US Open champion Coco Gauff faces fellow American Jessica Pegula in the other Orange Group match on Sunday.
