After seeing fellow American Brooks Koepka repeat as champion in the U.S. Open earlier this year, it is not out of the question for Thomas to follow suit here at Bellerive, which is hosting the PGA Championship for the first time since 1992.
For last year's victor Justin Thomas it's one thing to win it's another to repeat.
Day won the PGA Championship three years ago at Whistling Straits in Wisconsin.
That noise? It's softened considerably during the previous year, and the spotlight that accompanied him to Quail Hallow shines a little less brightly on Spieth in St. Louis.
As was expected, Tiger Woods was the centre of attention during media day at the PGA Championship.
"It's definitely something that's a big accomplishment and something that I'm very proud of", Johnson said of the No. 1 ranking. It's the fourth and final major of the year.
"It will always be circled to complete the career Grand Slam, which will ultimately achieve a life-long goal for me, so certainly emphasis in my head on it, but nothing overpowering", Spieth said.
Francesco Molinari was given the courtesy of a few questions about the impact of his historic British Open win at Carnoustie last month - the first major triumph by an Italian - but the media did not want to know how it felt to hoist the Claret Jug so much as what it was like playing the final round with Woods.
Englishman Tommy Fleetwood is a player who's seemingly in contention every week, yet he's still searching for his first victory on USA soil and his first major championship. But Nantz says it's tough to predict who will win.
This week is Woods' 19th appearance in the event since making his debut in 1997.
If nothing else, Spieth should have plenty of support this week.
"You can play this game competitively until you're close to 50". At the end of the day, a lot of careers are defined on major championships.
It would be even more fun to make history in front of them.
"I have put myself in contention in the majors".
"I'm sure Jordan feels a little bit different this week than he does the other three majors, but that's normal", McIlroy said. "It's going to be hot, it's going to be wet, and fortunately I'm one of the guys who hit the ball high and get the ball up in the air, and you just need to get the ball out there".