Golfers are bracing for what should be the most difficult golf tournament of the year at Oakmont this week, and early impressions of the ultra-thick rough and speedy greens suggest that the U.S. Open could see another winner over-par.

World No. 1 Jason Day spoke to reporters at Oakmont Tuesday and said that he's "never been more stressed" leading into the U.S. Open. Given the extremely punishing hazards, Day said he expects to avoid using driver too often this week.

"I think you can lay back here at this golf course. You can try and overpower it. There are some holes out there that you can hit driver and go after, but the rough is so thick, it's just a premium on hitting fairways this week. I think if you can dial it back a little bit, give yourself opportunities on the fairways, you're definitely at an advantage hitting a 7 iron rather than a wedge out of the rough this week. We always say each and every week, it's a bomber's course. For the most part, it's a bomber's game, our generation. It's not like that this week.

I played last Friday, and there was this shot that I hit ten feet out of the rough. You just cannot hit it in the rough in certain places, and I don't want to do that. So I'm going to try and do my best to hit the fairways and try and get it on the green the best I can."

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Day took a few months away from golf following his dominant end to the 2015 season, but said it was vital for him to avoid burning out.

"I had a very boring life, which is fine. I like being boring. I just hung out with the family. I had three months off. I played golf once, played four holes. I had an RBC thing I had to do down in Florida. Played four holes, went to the driving range. That was a month and a half into my stint, and then a month and a half went by. So it was three months total where I practically didn't pick up a golf club.

I went to the gym twice a day. I really tried to work on my nutrition, tried to work on my body for the upcoming season. But really tried to spend a lot of time with Ellie, Dash and Lucy."

The Day family has received plenty of airtime celebrating on the 18th green this season as Jason Day has already won three events in 2016. Day joked that his seven-month-old daughter Lucy is a "very big baby."

"People forget [Dash is] 3. He's a humongous toddler. He's very big. And you should see Lucy, she's even bigger. She's a fatty. It's fine. Like Ellie, I think she has protein shakes in those things. I don't know what she's doing. But for some reason, she's a very, very big baby. I don't know how other people have real tiny babies."