Australia's Day will be competing for the first time since his wire-to-wire victory in the US PGA Tour's Players Championship.
During his well-deserved break, McIlroy ended a six-month victory drought with a scintillating victory in the Irish Open, while Spieth shook off a Masters meltdown to win at Colonial Country Club on Sunday and edge closer to Day atop the world rankings.
For Day, the successes of his rivals are fuel for his own competitive fire.
"I heard a couple of weeks ago that it bothered Jordan that I was winning tournaments and have the number one spot in the world," Day said as he prepared for the Jack Nicklaus-hosted tournament at Muirfield Village in Dublin, Ohio.
