On the highway from Milwaukee out to the town of Kohler, which owes its name to the family that gave the world designer porcelain toilets before moving into the world of designer golf courses, there is a giant billboard featuring a beaming Rory McIlroy, the defending champion.

"This Is Major" is the catchline and this 97th edition of the US PGA Championship here at Whistling Straits is indeed a fitting finale to golf's season of Major championships.

Except the billboard really should have a second face: that of Jordan Spieth.

For in this golfing year, the 22-year-old Texan has emerged as a viable challenger to McIlroy to be the face of the sport. Spieth won the Masters, won the US Open and came within a whisker of getting into a play-off at the British Open. He, too, is a poster boy.

Two titles out of three for Spieth ain’t half bad, and that new rivalry of the ages between the two young guns is all the better for McIlroy’s return to action having missed out on his defence of the claret jug due to injury.

So it is that the PGA Championship, top heavy with firepower and featuring 97 of the world’s top 100 ranked players, gives us a showdown that will define who is really the best player on the planet.

And although this is far from a duel between just two men, Rory v Jordan/McIlroy v Spieth, whichever way you put it, it still has a magical ring to it.

Enthralling

But throw names like Jason and Rickie and Dustin and Bubba and Justin and Zach and Adam and Sergio into the mix, and the concoction becomes ever more enthralling. And what about Tiger? Or Phil? Or, for that matter, Shane? The truth is that the depth of contenders for the Wanamaker Trophy should this time make for quite the shindig on this contrived links by the shores of Lake Michigan.

"He's a master of illusions, and his golf courses take some time getting used to," said Justin Rose of the design concepts of Pete Dye.

And although it will be quite the challenge for players to stay out of the bunkers which form a tapestry around the dunes, there is also the belief it is a course that should suit long hitters who will also be helped by soft, receptive greens.

Of course, Spieth's name is the one bandied about for good reason in a season where he has been most dominant. "It's pretty impressive at such a young age how mature he is, how far he's come," said Australian Jason Day, something of a spring chicken himself at just 27 years of age: "Right now, his confidence is through the moon. Whatever he's doing right now, he needs to just bottle it all up and know this is a winning formula."

Momentum

Even McIlroy, when pushed, acknowledge that Spieth is the man to beat. Who is the best player in the world?

“If you were to go by this year, you have to say Jordan. I would say if you go over the last two years, it’s probably a toss up between Jordan and myself . . . it’s all a matter of opinion at this point,” said McIlroy, who has been world number one in the official rankings for 52 straight weeks.

McIlroy is one of five Irish golfers in the field, along with Shane Lowry, Graeme McDowell, Pádraig Harrington and Darren Clarke.

Lowry is seeking to maintain the momentum of his win in the WGC-Bridgestone Invitational

“You learn from your ups and you learn from your downs,” he said. “If I learned one thing last week it is that you have to keep going, you never know what’s around the corner. You are only ever one week away from greatness. To win a major is greatness. Winning a WGC is not far away.”

The Offalyman will take a six-week break after the PGA if he fails to claim a place in the FedEx Cup playoffs. He needs a top-five finish here to do so.

For McDowell, it is a case of taking what he calls “baby steps” towards contending in Majors again after a disappointing season that finally showed some promise in Akron.

“I can’t expect to all of a sudden jump up and win the PGA Championship. It is not out of the realms of possibility but I have got to set my expectations where they need to be. A top 15, top 20, something along those lines, would be a step in the right direction,” he said.

There are no such baby steps for Spieth. At 22, he is the second youngest player in the field and very much the man to beat.