A trio of golf spectators negotiate the muddy paths left by recent rains during a practice round at the 2013 US Open Championship at Merion Golf Club. (ERIK S LESSER/EPA)

The process of identifying the best player in the world, as the U.S. Golf Association says it aims to do annually, is an arduous task. Merion Golf Club, where the 113th U.S. Open will begin Thursday morning, has undergone two years of preparation for one week, and the 72 holes — at least — that lie ahead could well separate stout from soft.

But in the midst of that will be another factor: fortune, perhaps of the unprecedented variety. Merion is a 117-year-old marvel, interesting at every turn, but it also currently sits as a swamp after a week of downpours. And with Thursday’s opening round threatened by everything short of Armageddon — high winds, more rain, even the possibility of a dreaded derecho — almost every player in the field will find his ball at some point in a fairway caked with mud.

And in those instances, he will have little choice but to pull out a club, take a swing, and guess.

“All this theory about, ‘Oh, if the mud’s on the right it will go left and if the mud’s on the left it will go [right]’ — believe me, that’s a bunch of baloney,” said Lee Trevino, who won the 1971 Open here. “You don’t know where the hell it’s going to go when that mud is on there.”

No one argues over whether mud affects a golf ball’s flight. “If it’s a long shot, it literally can cost you shots,” said Graeme McDowell, who won the 2010 Open. The debate is about how to handle such situations and to what extent chance should determine the outcome of one of golf’s four majors.

On the PGA Tour, this would not be an issue. When fairways grow soggy in those tournaments, officials simply allow a procedure called “lift, clean and place,” which is fairly self-explanatory: If a ball is in the fairway, a player can mark the spot, pick it up, clean it off with a towel, and put it back within six inches of that spot, no nearer the hole. The USGA — which oversees this tournament and works with its British counterpart, the R&A, to draw up rules worldwide — all but deems such a practice as “lift, clean and cheat.”

“Most of you know that there is a local rule to adopt for preferred lies,” said Tom O’Toole Jr., the chair of the USGA’s championship committee. “That said, it’s been a long-standing philosophical point of view from the USGA to not adopt that local rule in our national championships. And the current championship committee is consistent with that long-standing philosophical point of view.”

Even with so much more rain in the forecast?

“If it was so bad, then the obvious response to that, or consequence, would be we probably wouldn’t be playing,” O’Toole said.

So, to review: No player will touch his golf ball between the time it leaves the tee and the time it reaches the green. Any questions?

Well, yes, some players have them, even while acknowledging the edge a “preferred lies” ruling allows.

“You can use that rule to your advantage,” McDowell said. “You can change your angle. You can get putter in your hand. You can get yourself out of interesting scenarios at times.

“But I think mud balls are a problem. I think they’re unfair. I think golf is designed to be played from a closely mown fairway. If you hit it in that fairway, you deserve a great lie and a great opportunity to attack the green surface. That’s the reward you get for hitting the fairway.”

At Merion, that reward should be significant, because the rough here will be as high as five inches. But how about this for some counter-intuitive thinking?

“It seems like a guy might be rewarded more for missing fairways in those situations, being in the rough,” said Matt Kuchar, who has won twice on tour this year, “not picking up the mud when you drive it in the rough.”

There are, of course, players who believe this should be a non-issue.

“That’s golf,” said David Graham, who won the most recent Open at Merion, in 1981. “It’s just the luck of the draw.”

But it can have a real impact. At the 2009 Masters — another tournament at which organizers don’t allow lift, clean and place — Kenny Perry was in a playoff with Angel Cabrera and came to his ball at the bottom of a hill in the 10th fairway. He found mud caked to the right side of his ball. He thought that would make his approach fly left, and told his caddie so.

“It’s a tough deal,” Perry said afterward.

“You don’t know quite what it’s going to do.”

The ball, indeed, flew left, but farther than Perry figured. He missed the green, made bogey, and lost the Masters.

Trevino, for one, put it on players to adjust to the conditions.

He said if mud balls are a problem — and this usually happens in the days after the rain, when the fairways start to cake up a bit — players shouldn’t hit the ball as high.

“I went so low that it cleaned itself before it stopped rolling,” he said. “You think that’s funny, but it’s true.”

But others argued that it’s not that easy anymore. Newer balls, argued Steve Stricker, are designed to spin less so that they launch higher. But with less spin, mud adheres more easily.

“Mud takes spin off,” Stricker said, “so it doesn’t take much mud to really affect that ball.”

Think about that as the rains fall Thursday at Merion, and wonder about it when there are errant shots from the middle of the fairway over the weekend. At some level, this is nothing more than pampered pros complaining about otherwise ideal conditions. At another, it could determine the outcome of the U.S. Open.

“We’re going to have to deal with it, I think,” Stricker said. “And yeah, it could decide who the champion is here this week, unfortunately.”