Sofia Kenin lost her first WTA match since winning the Australian Open earlier this month.
Sofia Kenin went down 6-7 (2/7), 6-3, 6-3 to Elena Rybakina on Tuesday at the Dubai Championships.
World number seven Kenin´s loss completed a hat-trick of seeded upsets on the fourth day of action in the United Arab Emirates.
Title holder Belinda Bencic overhauled 1-6, 6-1, 6-1 by Anastasia Pavlyuchenkova.
While, third seed and two-time tournament winner Elina Svitolina was hammered 6-2, 6-1 by qualifier Jennifer Brady.
American Kenin played a pair of non-Tour Fed Cup matches immediately after her Melbourne win over Garbine Muguruza, who cut short Kim Clijsters´ comeback on Monday.
The 21-year-old went down in just over two hours to her 19th-ranked opponent who stood 192nd in the world a year ago.
“There´s a bit more pressure coming from my side.
But I´ve just got to try to manage it for the next tournaments,” said Kenin.
“I just didn´t feel my game really well.
I just made too many unforced errors, I didn´t take my chances. I felt really off the whole match.”
Kenin got away to an early break but lost it and had to win the first set in a tiebreaker.
Rybakina then dominated the next two sets to reach the second round where she will face Russian Katerina Siniakova.
Kazakh Rybakina won the Hobart title in January and reached the final last weekend in St Petersburg.
“I prepared with good practice. I didn´t expect that I would win. I tried to do my best,” Sofia said.
“I wasn´t nervous (after flying here from Russia) at all because I knew it´s going to be tough.
“I didn´t think about that she just won the Australian Open, I know that now everyone can beat everyone,” she added.