OAKMONT, Pa. — Jason Day, it would seem, is on top of the golf world. He’s ranked No. 1, snagged his first major at last year’s PGA Championship, and has won seven times in his last 18 PGA Tour starts, a staggering accomplishment.

So why does Day say he’s under more stress than ever? Other than, you know, getting ready to play a US Open at one of the most challenging courses in golf?

“I’ve never been more stressed in my life than right now,’’ Day said Tuesday at Oakmont Country Club. “It’s just because being No. 1 in the world, having a lot of expectations on you, having to practice so hard to keep that No. 1 spot, trying to win as many tournaments as I can puts a lot of stress and pressure on your shoulders.’’

Day has been preparing for the US Open by playing and practicing. He’s already won three times this year, including the Players Championship, and of his 10 cuts made in 11 starts, he’s finished 11th or better seven times. He’s on form, and is the betting favorite to add the US Open this week.

But Day also makes a point of getting away from golf. He had a good reason late last year, after the birth of his daughter, Lucy, in November. He took three months off, limiting himself to four holes during a corporate outing. That was it.

“You can play golf pretty much every week if you wanted to,’’ he said. “But that just doesn’t work out that way because you’ll mentally fry yourself and you’ll be done.

“I think it also keeps you very hungry coming in because you see guys that have already played maybe 10 events in front of you.

“They’ve got such a big lead in the [points race] that you come out and you kind of put yourself into a bit of a corner where you have to force yourself to play well. So it’s a good thing.’’

A tough encore

Danny Willett and Jordan Spieth will always be intertwined, simply because of the way Willett won — and Spieth lost — this year’s Masters. But Spieth can understand the position in which Willett now finds himself: As Masters champion, he’s the only one this year who can win the grand slam. Spieth followed his Masters win last year with a victory in the US Open.

Willett isn’t making any predictions. But he also won’t acknowledge that the glow of winning this season’s first major is gone before he begins the second.

“I don’t think it will for a while. It’s still a great achievement. We had a few weeks celebrating and stuff,’’ said Willett, who missed the cut at the Players after winning the Masters, and has had two top-25 finishes on the European Tour, including a third at the BMW PGA Championship, that tour’s flagship event.

“I know no one’s done it. I honestly can’t see it happening, just purely because of the strength and depth of the field.’’

Back to school

Phil Mickelson was not at Oakmont Tuesday. He was attending an eighth-grade school graduation for his daughter, Sophia, in California. Mickelson flew home after practicing at Oakmont Monday, and is expected back Wednesday. He did something similar in 2013, when the US Open also was held in Pennsylvania, at Merion. Mickelson tied for second that year, the record sixth time he’s been runner-up in this tournament . . . Branden Grace is a big fan of Oakmont. Just not of the first hole, a downhill par-4 with a scorecard yardage of 482. “The first hole is just a terrible golf hole; it is,’’ said Grace, who tied for fourth last year at Chambers Bay, then finished third at the PGA. “If you stand on that tee and the wind’s left to right, that fairway is so thin, so narrow that you kind of almost only see bunker. That first hole, I think, can really get into somebody’s head. If you make a double or a triple, which is very easy to do, then your day is just going to be even longer than what it was going to be before that hole.’’

They were thereMickelson is one of four players this week who played at Oakmont in the 1994 US Open (he tied for 47th). The others: Ernie Els, who won that event, Jim Furyk (T28), and Jeff Maggert (T9).

Twenty-eight of the 156 players competed in the 2007 US Open at Oakmont.

Michael Whitmer can be reached at mwhitmer@globe.com. Follow him on Twitter @GlobeWhitmer.