THE US Open is traditionally the toughest challenge in all of golf, but one PGA Tour veteran thinks Erin Hills might be unfairly difficult.

Kevin Na posted a video to his Instagram showing off the punishing fescue at Erin Hills, which is just a few yards off of the fairway. Players who hit in into the long grass will pay a severe penalty, and according to Na, they might not find their ball at all.

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“You’ve got three to four yards of rough, maybe five at the most, then you’ve got fescue.

I’m going to throw a ball in there. I threw it three yards. Now you’re lucky if you find your ball. I just moved grass and I found it. I’m going to play out of here. Every hole we’ve got this.

[Takes swing]. Nope, didn’t move.

[Takes another swing]. Moved a foot. Now I can’t find it.”

If you take a look at Na’s replies on Instagram, most fans are telling Na to “just hit it straight” and “stop whining.” It’s not that simple.

Erin Hills is listed at 7,741 yards (7078m) – the longest in U.S. Open history, with multiple holes over 600 yards and up to five par-4s over 500 yards depending on tee placement for the day.

Players can’t afford to avoid trouble by hitting a safe driving-iron or metal off the tee box in many cases, meaning the fescue will be in play even for the best drivers on tour.

Na’s point about struggling to even find his ball raises another issue. If players who hit into the rough have to spend a few minutes just to search for their ball, it won’t take long for traffic jams to form on the course, meaning more sitting around and waiting for the course to clear in front of you.

Adam Scott voiced his concern over recent U.S. Open setups a few weeks ago at the Memorial.

“Let’s just have something that’s a challenge and interesting, not just playing brutal,” he told Golf.com.

“The ball is in their court. Hopefully they get it right this time, just from a playability standpoint.”

To put it simply, there will be a lot of agitated golfers in Wisconsin this week.

Steve Stricker of the United States plays his shot from the fifth tee during a practice round. Source: AFP

“It’s one of the toughest mental tests that you’re going to encounter out there, and it’s important to be fresh, and at least I think I’ve got that part,” British Open champion Henrik Stenson of Sweden told reporters on Monday.

“I’ve had a week off in Sweden and haven’t really focused much on golf. So at least we’re fresh.

Spain’s Jon Rahm, a candidate to become the sixth successive first-time major winner, said he also was trying to lessen his stress level before Thursday’s start.

“I wanted to get some rest at home, work out, practise on my game. And made sure I stayed patient, not get the anticipation built up too high.” Rahm, who tied for 23rd as the low amateur at last year’s US Open at Oakmont, has been a sensation since turning professional.

He won the Farmers Insurance Open in January and has recorded five more top-five finishes to zoom up the world rankings to number 10.

Rahm played a full round of practice on Monday and was full of enthusiasm.

“I absolutely love the golf course,” he said. “It’s a very long golf course, big greens. ...It’s like a links golf course on steroids.” The Spaniard said he plans to dial down his practice to stay fresh. “Played 18 holes today to get a feel of the golf course. I’ll play nine tomorrow and nine Wednesday, and after the nine holes try to get my touch around the greens which I think will be very important,” he said.

The greens, like the fairways, are full of slope. Although there is no rough around the greens, swales can carry errant approach shots far away from the pins.

Stenson took a different approach to getting acclimatised.

“It’s important to have your mental strength and energy over the weekend, if you’re going to do well, and not overdo it in the first couple of days,” said Stenson, who added the Olympic silver medal in Rio.

“So I walked 18 today, and then I’ll play nine tomorrow and nine on Wednesday and that should be good,” Stenson said in between sneezes.

“One thing I forgot to say, this is hay fever heaven, and I expect any local pharmacy to sell out of antihistamines. If you haven’t gotten yours, make sure you get them quickly.

“I forgot to take my pills this morning and I’ve been sneezing about 50 times already.”

This story originally appeared on Fox Sports US.