Watson did not drop a set in confirming her place in the main draw
British number three Heather Watson was beaten 5-7 6-3 7-6 (7-3) by Christina McHale in the first round of the Family Circle Cup in South Carolina.
The 18-year-old from Guernsey had beaten Josephine Kuhlman and Lenka Wienerova to reach the main draw.
Watson was 4-1 ahead in the deciding set against American McHale, the world number 97, her former doubles partner.
But McHale forced a tie-break in which she raced 3-0 ahead and sealed a hard-fought victory in two hours 51 minutes.