Second seed Garbine Muguruza suffered a shock 6-3 6-2 defeat to Jana Cepelova in the second round of Wimbledon on Thursday.
Muguruza was a runner-up at the All England Club in 2015 and came into this year's competition on the back of a first grand slam triumph at the French Open.
However, her hopes of successive major victories came to a premature end at the hands of the world number 124, with an error-strewn display sending her out in just 58 minutes.
Cepelova eliminated Simona Halep on this court last year and she appeared to take confidence from that, mounting an aggressive start which secured an opening break.
The Slovakian qualifier frequently changed the pace of her attacks, exemplified when a brilliant cross-court slice put her into position to serve for the set.
Cepelova required two attempts to do so, sending a forehand winner deep into the corner, and her momentum continued in the second set.
The 23-year-old raced into a 4-0 lead before Muguruza held to love, but she failed to take advantage of two break points in game six.
Cepelova will now meet Lucie Safarova in the third round, while Halep and Angelique Kerber's hopes of making the final have been boosted by Muguruza's exit from the bottom half of the draw.