CHARLOTTE, N.C. -- Vijay Singh withdrew from the Wells Fargo Championship because of a sore back Wednesday, one day after the PGA Tour said it would not punish the Fijian for his admission that he used deer antler spray.
The tour said Tuesday the World Anti-Doping Agency informed it that the spray contains only small amounts of a growth hormone factor that is banned under the anti-doping policy.
The tour had been set to sanction Singh until WADA clarified its position on deer antler spray.
The 50-year-old Singh, a past champion at Quail Hollow, is among several players who have withdrawn this week.
He declined to comment to a PGA Tour media official Tuesday after the tour dropped his case on the anti-doping violation. Singh has not spoken to reporters since he released a statement in late January that said he was shocked to learn the deer antler spray he had been taking might contain IGF-1, which is on the banned list.
Singh admitted to taking the spray in a Sports Illustrated story, which also linked Baltimore Ravens linebacker Ray Lewis to the product.
PGA Tour Commissioner Tim Finchem said Tuesday that while admission is tantamount to a failed drug test, WADA informed the tour late last week that it no longer considers the use of deer antler spray to be prohibited except for a positive test result.
The tour said it tested the spray that Singh provided, and it showed a presence of IGF-1. WADA subsequently told the tour that IGF-1 is known to contain small amounts of the hormone factor.
''I don't know of a substance or a transfer mechanism out there that can load a person to IGF levels that would get the attention of the WADA science people,'' Finchem said Tuesday. ''Clearly, this isn't one. They've made that clear to us.''
Singh's case had the attention of PGA Tour players for the last three months, and it ended with a peculiar twist.
''Clearly, it was the right decision based on the information we have today,'' said Joe Ogilvie, a member of the Player Advisory Council. ''Players just have to be very careful whenever they pay more than $3,000 a month for supplements. That's the lesson to be learned.''
Rory McIlroy also agreed with the outcome, saying that WADA's decision meant there was little the PGA Tour could have done.
''Look, my stance on it is Vijay didn't know he was doing anything wrong,'' he said, ''and if there's no intention there, then I don't see any reason to unfairly punish him.''