By Nick Mulvenney SYDNEY (Reuters) - Local amateur prospect Curtis Luck and compatriot Lucas Herbert shot five-under-par 67s for a share of the lead as Jordan Spieth struggled with his putting in the opening round of the Australian Open on Thursday. Luck, the U.S. and Asia-Pacific Amateur champion, mixed seven birdies with two bogeys to upstage playing partners Spieth (69) and former U.S. Open champion Geoff Ogilvy (70) after their early morning tee-off at a sunny Royal Sydney. World number five Spieth, winner of the Stonehaven Cup two years ago, managed just one birdie on his front nine but three more after the turn kept him well in contention despite a bogey after driving through the green on his penultimate hole.
