British Open champion Phil Mickelson has declined an invitation to play in this year’s Grand Slam of Golf at Port Royal.The PGA of America, who organise the tournament which features the year’s four major winners, made the announcement today, citing a ‘scheduling conflict’ for the American’s absence.Details of that conflict haven’t been revealed.As Masters champion, Mickelson has previously foregone the chance to play in the Slam in Bermuda.He will be replaced by Padraig Harrington who will make his fourth visit to the Island. He won last year’s event and finished runner-up in 2007 and ’08.This year’s field includes Masters Champion Adam Scott, US Open Champion Justin Rose and PGA Champion Jason Dufner.The 36-hole event will be played at Port Royal on October 15-16, preceded by a Pro-Am on October 14.