The world's No. 1-ranked golfer slipped on wet concrete, aggravating a previous injury to his left knee, he revealed in a statement, adding that he was advised to withdraw and head home for further tests after consulting with his doctor.
Koepka sat at even par through 36 holes. He shot a 3-under 69 in Round 1 before posting a 3-over 75 in Round 2.
The 29-year-old won the South Korea-based event by four strokes in 2018.
He had stem cell treatment performed on his left knee during the offseason and was off to a slow start to begin this campaign, having missed the cut at the Shriners Hospitals Open earlier this month.