Vijay Singh withdrew from the Phoenix Open on Thursday, a day after saying he used deer-antler spray and was "absolutely shocked" that it may contain a banned substance.
Singh cited a back injury in pulling out before the first round.
The 49-year-old Fijian paid one of the owners of Sports With Alternatives To Steroids $9,000 last November for the spray, hologram chips and other products, said Sports Illustrated.
The magazine also reported Baltimore Ravens linebacker Ray Lewis sought help from SWATS in his recovery from an arm injury. The company says its deer-antler substance contains a banned performance-enhancer connected to human growth hormone.
Singh said in a statement on Wednesday that while he used deer-antler spray he was not aware he may have been violating the U.S. PGA Tour's anti-doping policy.
"I am absolutely shocked that deer-antler spray may contain a banned substance and am angry that I have put myself in this position," he said.
He was cooperating with a tour investigation.
Singh, a three-time major champion, won the last of his 56 titles in 2008. Early in his career, he was suspended from the Asian Tour for two years for altering his scorecard during a tournament in Indonesia.