Sofia Kenin of the US plays against Kazakhstan's Elena Rybakina during the WTA Dubai Duty Free Tennis Championship, at the Dubai Tennis Stadium in the United Arab Emirates, on Feb 18, 2020. (KARIM SAHIB / AFP)

Australian Open champion Sofia Kenin says she is frustrated by her inability to rediscover the rhythm that secured her a maiden Grand Slam title at Melbourne Park after the American crashed out of the Qatar Open.

The 21-year-old suffered a 6-3 7-6(4) second-round defeat to Ukrainian teenager Dayana Yastremska on Tuesday. Last week, Kenin fell at the first hurdle against Elena Rybakina in the Dubai Duty Free Tennis Championships.

Honestly, it's just finding my rhythm again. I feel like I'm completely out of it

Sofia Kenin

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"Honestly, it's just finding my rhythm again. I feel like I'm completely out of it," Kenin, told the WTA website here.

“It’s really frustrating. Obviously coming off of Melbourne, where I felt I was playing the best tennis of my life, coming down to playing, not the worst, but not playing the tennis I want to be playing.

“She (Yastremska) played better at important moments and I made too many unforced errors, I just felt pretty flat footed the whole match ... I feel like I can’t find my game.”

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Kenin is back in action at Lyon next week before she returns to the United States for the Indian Wells and Miami tournaments.

Top-ranked Ash Barty, Australian Open runner-up Garbine Muguruza and former world number one Karolina Pliskova all advanced to the next round in Qatar.