Jordan Spieth didn't take long when asked for one word to describe a U.S. Open course where trains rumble loudly by, holes can change from one par to another, and players sometimes search for little white markings to see if they're actually on a green.

"Inventive," the Masters champion said.

That may not be the word some players will be using when play gets underway Thursday on a course unlike any other in Open history. Chambers Bay isn't for the faint of heart, or those without some imagination in their game.

But if the grumbling is to begin, the Masters champion wants no part of it.

"If you are going to talk negative about a place, you're almost throwing yourself out to begin with because golf is a mental game," Spieth said.

Indeed, the player with the best game doesn't always win the Open, where par is jealously guarded by the USGA. But while Spieth and Rory McIlroy are the favorites of the oddsmakers in Las Vegas, no one is really certain about anything on a golf course that will change by the day.

Except that patience — like in any Open — figures to be a big key.

"I keep saying to people, the U.S. Open is all about controlling your attitude, controlling your emotional level and your stress levels out there because it can be a very frustrating week if you let it be," Jason Day said. "You've just got to keep grinding and grinding and grinding, and hopefully by Sunday you're somewhere around the lead."

The links-style course built on an old gravel pit may end up the star of this Open, no matter who ends up conquering it. Chambers Bay — with its one tree and huge elevation changes on the edge of the water will look good on television, even if the players don't.

Some won't be able to adapt to hitting shots 20 yards away from where they want their ball to finally come to a rest. Others will have difficulty judging tee shots that will hang in the air longer than usual.

And some might have trouble just finding the greens, which are the same fescue as the fairways and seem to blend in with them on some holes. The USGA is trying to help out by painting little white dots around the greens to show where they are.

"I think it might be slower rounds of golf, given the size of the greens and the difficulty of the course," Spieth said. "(But) at least we have some nice views."

The views were already there when architect Robert Trent Jones Jr. went to work on building the course that opened to the public in 2007. So were the elevation changes, and the train tracks that run between the course and the water.

What Jones did was take it a step further with fine fescue grass throughout and holes with so many tees that two holes — No. 1 and No. 18 — can be switched from par 4's to par 5's and back again during the week.

It's a place unlike any some players have seen, and it will take some getting used to.

"Those who adopt it and embrace it, they like it," Jones said. "Those who are uneasy with the newness of it, we'll listen to them, but they probably won't make the cut."

USGA executive director Mike Davis said in April that players will have to study the course carefully to have a chance of winning. Just playing a few practice rounds, he said, won't be enough to figure out its complexity.

Spieth, who shot an 83 when the U.S. Amateur was held at Chambers Bay in 2010, has done just that, including a few extra rounds over the weekend to figure out where the ball will be rolling on what will surely be a fast and tricky track.

Still, it's the U.S. Open and it will be a grind. Spieth is only playing his fourth Open, but understands that if he is going to get halfway to a Grand Slam, he has to be as prepared mentally as he is physically.

"You have to go in positively," he said. "You have to go in with enough confidence to get yourself into contention."

For some players this week, that might be the toughest thing of all.