Matt Kuchar suffered a late slump to surrender the lead in the third round of the Humana Challenge.
South Africa's Branden Grace won the Commercial Bank Qatar Masters by one shot from Marc Warren of Scotland on Saturday.
Ryan Palmer carded a superb 61 but it was Matt Kuchar who took the lead at the halfway stage of the Humana Challenge.
American Dustin Johnson denies he has had a drug problem but admits "drinking to excess" was an issue he had to address.
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