Leading 5-1 in the third set and on the cusp of the biggest victory of her career, 81st ranked Osaka crumbled as Keys swept the next five games en route to a victory that left her stunned 18-year-old opponent fighting back tears.
It was an excruciating collapse played out on the game's biggest stage.
The Japanese world number 81 was left in tears several times as her lead slowly slipped away, a distraught Osaka at one point hanging her head and covering her eyes as she walked to a corner of the court.
But there was no place to hide inside the massive Arthur Ashe Stadium from the gaze of thousands of fans or a ruthless Keys who moved in for the kill clinching the comeback when Osaka sent a return wide.
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(Editing by Frank Pingue)
