By Tony Jimenez TROON, Scotland (Reuters) - Jason Day is unconcerned about the threat being posed to his status as world number one by Dustin Johnson, Jordan Spieth and Rory McIlroy - for the Australian it is all about "conquering my ego". It was his display in the 2015 British Open that gave Day the belief to launch a barnstorming run to the top of the rankings and now, 12 months on, he would like nothing more than to triumph at the world's oldest major for the first time. The U.S. PGA Championship winner is certainly not fretting about the possibility of having to eclipse second-ranked Johnson, number three Spieth or fourth-ranked McIlroy in a head-to-head duel in Sunday's closing round at Troon. More...