Sungjae Im withdrew from the CJ Cup Byron Nelson prior to his opening round due to illness, the PGA Tour announced on Thursday.
Im, 26, successfully defended his title at the KPGA Tour's Woori Financial Group Championship last week in his native South Korea. He was scheduled to be part of a featured group that included defending champion Jason Day and Jordan Spieth at TPC Craig Ranch in McKinney, Texas.
Im will be replaced by S.Y. Noh, who got off to a fast start with a 60 at last year's tournament before limping to a tie for 74th place.
Also on Thursday, Russell Knox withdrew for an undisclosed reason. The two-time PGA Tour winner was replaced by Scott Piercy.
Knox had been named as a replacement earlier Thursday following the withdrawal of Sean O'Hair.
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