Springfield - World No 1 Jason Day and US Open champion Dustin Johnson top a host of on-form players in golf's strongest field since 1986 when the 98th PGA Championship starts on Thursday.
The showdown at Baltusrol has the toughest lineup based upon the world golf rankings since they began 30 years ago, with Day defending his first major victory from last year at Whistling Straits, where he set a 72-hole major low score matched by Sweden's Henrik Stenson to win the Open Championship two weeks ago, both going lower than Tiger Woods ever did.
"Any number of guys can turn up on a major championship week and win," world No 4 Rory McIlroy said. "You're looking at Henrik getting to 20-under two weeks ago, Jason getting to 20-under at Whistling Straits last year.
"Do I feel like I'm playing five or 10 Tigers out there? No. I feel like that would be disrespectful towards Tiger. But the fields are deeper and so many guys have chances to win."
Australian Day, trying to match Woods as the only back-to-back PGA winner since the event adopted stroke-play format in 1958, comes in with only one practice round and fighting illness as well as expectations.
"The bar has been raised ever since Tiger Woods came around," Day said of the 14-time major winner out for the season after back surgery.
"Everyone expects if you're in the lead or you're a favorite to win, they expect you to win, and if you don't, then you're in a slump. It's not the case. I think the bar has been raised. Once again the competition has got tougher."
"Guys are just younger and stronger and fitter and faster and longer. If you don't stay one step ahead of the young guys, it's easy to get left behind."
Jordan Spieth turned 23 on Wednesday (July 27).
If he wins the Wanamaker Trophy, he would be the youngest PGA Championship winner since Tom Creavy in 1931 at age 20. Gene Sarazen set the record by almost two months when he won at 20 in 1922.
Second-ranked Johnson, 32, can overtake Day for world number one with a victory or runner-up finish.
"If I'm on top of the leaderboard and I get to number one, obviously that would be great and be a big accomplishment," Johnson said.
Johnson has 12 top-10s in 17 events this season, including his major breakthrough at Oakmont, and he has the long-drive game to challenge back-to-back closing par-5 holes for possible eagle-eagle finishes.
"Unless the course firms up a little bit, 17, it's just a little bit too soft," Johnson said. "It's not really doable, unless it firms up. And 18, yes, everybody is going to reach 18."
Look for the PGA of America to make the 649-yard 17th, the second-longest hole in PGA Championship history, tempting for some.
"You always know in the back of your mind we have two par 5s to finish," said PGA managing director Kerry Haigh. "Hopefully there are scoring opportunities."
Stenson has the rare opportunity for two major wins over three weeks, saying, "When you've got the momentum and you're playing well, it might not be bad to get straight back at it."
Spain's Garcia, 36, will make his 73rd attempt to win his first major after sharing fifth at the US and British Opens.
"My swing wasn't quite there but I scrambled well," Garcia said of his effort at Royal Troon. "I guess for me that's positive because it shows I don't need to be perfectly in form to still have a chance going into majors."
Phil Mickelson, a US left-hander with five major titles, is on the course where he won the 2005 PGA.
"Lefty" would be the fourth-oldest major winner with a victory this week at 46 years, one month and 15 days.
Only Jack Nicklaus from the 1986 Masters and Old Tom Morris from the 1867 British Open, both 46, and record-holder Julius Boros, 48 at the 1968 PGA, would have won a major older.