World number one Caroline Wozniacki suffered a shock straight-sets defeat to 19-year-old Christina McHale at the Cincinnati Open.
The Dane was outplayed from the start, as world number 76 McHale took the first set 6-4.
The American delivered again in the second, while Wozniacki hit a number of unforced errors to concede the set 5-7.
McHale will face Nadia Petrova in the third round.
