ERIN, Wisconsin (Reuters) - Coming to relatively new Erin Hills, which is hosting its maiden major championship, gives the world’s best golfers a taste of the unknown this week at the U.S. Open.

Jun 12, 2017; Erin, WI, USA; Detail view of an Erin Hills logo golf ball for the U.S. Open golf tournament at Erin Hills. Mandatory Credit: Rob Schumacher-USA TODAY Sports

But being a U.S. Open, players can expect a mental and physical challenge at the year’s second major. The 11-year-old, tree-less course 35 miles (56 km) northwest of Milwaukee stretches beyond 7,700 yards, where calf-length fescue grass waves in the wind alongside fairways.

“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, practice 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 U.S. 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 acclimated.

“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.”