Leona Maguire opened her T-Match Play group with a heavy 6&5 defeat to Canadian Brooke Henderson at Shadow Creek, Las Vegas.
The Irish woman, who will face Jin Young Ko and Peiyun Chien in Group 8, will need to win her two remaining matches to be in with a chance of reaching the knockout stages.
The tournament sees a field of 64 pitted into 16 groups of four, with the four players in each group facing off over three days.
The group winners will compete in the Round of 16, with the quarter-finals also taking place on Saturday. The semi-finals and final are set for Sunday.
Maguire was on the backfoot from the off as Henderson went three-up after the opening four holes. The Canadian took the sixth, 11th and 13th to wrap the match up with five holes to spare.
Nelly Korda is the reigning champion having defeated Maguire in last year's final.
