SCOTTSDALE, Ariz. -- Vijay Singh has withdrawn from the Waste Management Phoenix Open, a day after saying he used deer-antler spray. Singh cited a back injury in pulling out Thursday before the first round. The 49-year-old Fijian first revealed he used the spray in an interview with Sports Illustrated. The magazine said Singh paid one of Sports With Alternatives To Steroids' owners $9,000 last November for the spray, hologram chips and other products. The deer-antler substance contains a banned performance-enhancer connected to human growth hormone.