Marta Kostiuk lost to Jessica Pegula and lost her chances of leaving the group of the WTA Finals tournament.
The match ended in two sets - 2:6, 5:7. Kostiuk committed nine double faults in the game.
The second defeat leaves Kostyuk in last place in the team standings. The Ukrainian lost her chances of finishing among the first 2.
Kostyuk will close out her WTA finals debut against Coco Goff on Thursday, November 12.