Rory McIlroy and Jordan Spieth: Golf's hottest rivalry

By the time 21-year-old Spieth was celebrating under a gorgeous Puget Sound sunset, Tiger Woods had long ago left the scene having missed the cut while Phil Mickelson, six times a runner-up at the U.S. Open, finished well down the leaderboard in a tie for 64th alongside a few other of golf's golden oldies like Angel Cabrera and Colin Montgomerie.

With 26-year-old Northern Irishman Rory McIlroy in possession of the British Open and PGA Championship, Spieth holding the U.S. Open and Masters titles and Rickie Fowler (26) winning golf's unofficial fifth major the Players Championship, the sport has taken on an undeniable youthful vibe as the greats who dominated the game for two decades fade into the background.

At Chambers Bay Woods, Mickelson and Ernie Els proved they can still attract a crowd but those fans appeared more interested in a trip down memory lane than the huge galleries packed with young men and women following Spieth and McIlroy.

McIlroy thrilled the Sunday throng with an early morning charge up the leaderboard before Spieth took over the spotlight scrapping to a one shot win over Dustin Johnson to become just the sixth golfer to win both the Masters and U.S. Open titles in the same year.

"It's kind of cool. I think to have two players hold the four majors and Ricky having the fifth," smiled Spieth. "It's awesome that the game is in young hands.

"I don't think much of a rivalry.

"Rory has four majors and dozens of wins and I'm just starting out.

"I'm just happy to have this and to be chasing that number one spot which he holds."

Whether Spieth and McIlroy are willing to embrace the idea of a rivalry or not the Texan and Northern Irishman are already being hyped as the new Tiger and Phil or Jack (Nicklaus) and Arnie (Palmer).

Certainly all the elements are in place for an enthralling battle.

The two men from two different continents hold the top two spots in the world rankings, McIlroy number one and Spieth number two, own all four major titles and could face each other for a gold medal at next year's Rio Summer Olympics.

But the ultimate test of any great rivalry is how it stands up over time and Spieth and McIlroy are just getting started.

The next chapter will be written at next month's British Open where Spieth will try to get his hands on McIlroy's Claret Jug and move one more step closer to one of the greatest feats in sport - a grand slam.

"I think it's in the realm of possibility," said Spieth. "I think that the Grand Slam, I think that -- I'm just focused on the Claret Jug now.

"I think that the Grand Slam is something that I never could really fathom somebody doing, considering I watched Tiger win when he was winning and he won the Tiger Slam, but he never won the four in one year.

"This (Chambers Bay) was somewhat of a British-style golf course, so are the next two majors. I've proven to myself that I can win on a British-style golf course now.

"Now I take it to the truest British-style golf course of any in the world and I'm not going to think about what could possibly happen after."