'I hated to leave, but I have a relationship with Byron that goes back a long time,' said Roberts, who won the PGA TOUR's Byron Nelson Classic in 1999.'He was a great man, the last of the great players of that era. He was a great gentleman. I just feel like I need to be there.'
Nelson died Tuesday at his ranch in Texas. He was 94. A funeral service is planned for Friday in Richland Hills, Texas.
Roberts, who has won four Champions Tour events this season, informed tournament officials of his withdrawal Wednesday night.
The move could drop Roberts from atop the Champions Tour standings. Jay Haas, the Greater Hickory Classic's defending champion, is currently No. 2 in both points and earnings and can become the tour's No. 1 player with a top-six finish.