And while McIlroy remains somewhat tight-lipped on who will caddy for him post the PGA Championship, he says he has received almost 50 emails from Tour caddies and regular Tour club pros seeking to caddy for the four-time Major victor.
As McIlroy was speaking, the European Tour announced that its flagship BMW PGA Championship would be moving from May to September in 2019. If Day's putter can get hot like it was over the past two seasons, he could be in line to win his second major.
"That there is going to cut the field in half", Johnson said.
Spieth had a short break after The Open and finished tied for 13th in the WGC Bridgestone Invitational last weekend.
China's Li Haotong looks on during a PGA Championship practice round at Quail Hollow Club on Monday.
"I think the changes are really good", McIlroy said.
"I feel like a 3-iron might be a pretty important club for me with a couple of the par 5s this week, and the sixth hole being such a long par 3", McIlroy said.
McIlroy isn't the only player trying to make sure the year doesn't end without him winning a major.
In terms of Spieth, he feels that winning his second major for 2017 will be tough as he is still scratching around for the ideal performance. There will be $10.5 million paid out to the competitors at Quail Hollow in Charlotte, NC.
Quail Hollow returned to the PGA Tour schedule in 2003, though it went through some dramatic changes in recent years.
Since he won his second PGA Championship and fourth major in 2014, McIlroy has seen Spieth, Jason Day, Danny Willett, Dustin Johnson, Henrik Stenson, Sergio Garcia and Brooks Koepka have their breakthroughs.
Tough at the top: It has been 10 years since the No. 1 player in the world won the PGA Championship. "He's playing well and he hits it plenty long to contend around here". "You've just got to deal with them, and you know, I feel like the golf game's in really good shape right now".
Asked what odds he'd give himself, McIlroy cited two wins in eight starts at Quail Hollow - "8-2, decent odds". I'm going to play to win.
He finished joint-46th at the US Open, and a week earlier at the beginning of June, finished joint-15th at the Memorial Tournament, both respectable performances. A lot of the courses that are set to host the PGA Championship over the next few years are all northern locations, such as Oak Hill in Rochester, NY, Bethpage Black, Whistling Straights in Wisconsin and Hazeltine National in Minnesota.