Day recovered from an early deficit to take a three up lead with three to play against the tough Englishman who boasts a great record in match play but bogeys at the 16th and 17th saw the match reach the 18th hole.
Day produced a brilliant recovery from the greenside bunker at the last, holing a 12 foot par saving putt to win the match 1 up.
Day had been beaten in the morning semi final by Matt Kuchar after holding an early lead. Kuchar won 4&3.
Day will earn a cheque for US$600,000 and move back perhaps as high as 25 in the world ranking.
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