“Mum and our entire family would like to thank all of our friends and supporters who have reached out in an incredible outpouring of love during such a difficult period. We are praying for her recovery,” the Australian world number three said in a statement on Friday.
Day, who as recently as last month was still ranked number one, pulled out of his opening match in Austin after six holes to be with his mother.
"Hard to comprehend being on the golf course right now, with what she's going through,” a tearful Day told reporters.
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Day did not say at the time how long he would be away from the game or whether he planned to compete at the April 6-9 Masters, the first major of the year.
"Emotionally, it's been weighing on me," he said. "My mum says not to let it get to me, but it really has so I just need some time away to make sure everything goes well."
(Reporting by Larry Fine in New York; Editing by Andrew Both)
