Garbine Muguruza suffered a shock loss to qualifier Karolina Muchova in a huge upset at the US Open.

Muguruza was beaten 3-6 6-4 6-4 by Muchova, the 22-year-old Czech who came through qualifying in New York, in the second round.

Playing in the main draw of a grand slam for the first time, Muchova completed her victory just after 01:00 local time (05:00 GMT) on Thursday.

Muchova, the world number 202, held her nerve in the third set, hitting 14 winners and just 11 unforced errors.

The loss marked two-time grand slam champion Muguruza's third second-round exit at majors this year.