Defending champion and top-seeded Venus Williams has lost 6-7 (4), 6-3, 6-2 to Russian teenager Daria Kasatkina in the first round of the ASB Classic.
The 18-year-old Kasatkina, ranked No. 75 and the third-youngest player inside the top 100, was handed a wildcard in recognition of her potential and fulfilled that promise with a win over the No. 7-ranked Williams.
Williams contributed to the defeat with 73 unforced errors.
After losing the long first set, Kasatkina matched Williams from the baseline and curbed her own errors to take the second, then rallied from 3-1 down to win the decider, gaining the vital service break in the seventh game and breaking again in the ninth.
"I couldn't ask for a better start to the year," Kasatkina said. "It took all my power."