David Drysdale has taken a share of the lead after day one of the BMW PGA Championship at Wentworth.
The Scot hit seven birdies as a round of 66 left him on six-under-par with Ireland's Paul Lawrie.
Donald needs to finish in the top eight at the tournament to regain his world number one ranking from Rory McIlroy.
Northern Irishman McIlroy endured a disappointing opening round as five bogeys and a double-bogey on the 16th left him on two-over-par.
His frustration was revealed on the 12th when he threw his club away.
McIlroy's fellow countryman Graeme McDowell also posted a score of two-over after a two-shot penalty.