Pretty much from the get-go at the U.S. Open on Monday, Madison Keys could tell she wasn't hitting the ball well or feeling very much at all like the self-confident player who claimed her first Grand Slam title at the Australian Open in January.

Australian Open champion Madison Keys was undone by 89 unforced errors and was upset in the first round of the U.S. Open by Mexico’s Renata Zarazua on Monday.

After 89 unforced errors, including 14 double-faults, the sixth-seeded American was gone from Flushing Meadows with a loss to 82nd-ranked Renata Zarazua.