Australian Open champion Sofia Kenin has become the third top-five seed to lose in the opening round of the WTA event in Dubai.
Contesting her first tour-level event since claiming her first grand slam title at Melbourne Park, American Kenin lost 6-7 (2-7) 6-3 6-3 to an Elena Rybakina.
"I just made too many unforced errors. I just didn't take my chances," Kenin said.
"I really thought I could have somehow turned it around. ... It's obviously really upsetting and disappointing at the moment."
Her opponent Rybakina has made three finals in the four tournaments she played this season, and is up to No.19 in the world, compared to 192nd this time last year.
"I'm so happy with my win today, I think today I followed the right tactics, that was the key to the win," Rybakina said of the high-level two-hour clash.
Kenin's exit followed that of third-seeded Elina Svitolina and Swiss fourth seed Belinda Bencic.
Ukranian Svitolina was ousted 6-2 6-1 by American Jennifer Brady while Anastasia Pavlyuchenkova defeated Bencic 1-6 6-1 6-1.
Kenin was broken by Rybakina while serving for the opening set but still took it in the tibreaker on the 47-minute mark.
Her Russian-born Kazakh opponent broke twice late in the second set to force a decider.
Rybakina found some powerful returns to get a crucial break for 5-3 in the third and nothing could stop the 20-year-old big-server from securing her seventh three-set victory of the year.
Australian Associated Press