Jason Day played yet another practice round with Tiger Woods on Monday at the U.S. Open. He thinks Woods is close to be a dominant again, although he added one caveat.

And it's a big caveat.

"Tell you what, if he could get on the fairway, he'd probably be back to where he was," Day said. "His iron play is just ridiculous how good it is right now. It's really special. The driver and the 3-wood ... the 3-wood is OK, the driver gets a little wide sometimes. But I think that's the biggest thing for him right now is to really kind of get on the fairway. His short game looks pretty good."

The fairways are the widest of any U.S. Open, though there is plenty of trouble because of the slopes and contours and massive bunker complexes.

More telling about the driver, however, is that Day wondered about Woods' desire or whether he was troubled by anything off the golf course.

"You could have all the tools in the world, but if you really don't want to be there or if there's something that's off course that's playing on your mind ... the game of golf is so mental and if you don't have everything in the right order, it's very difficult to win golf tournaments," Day said.

"I've learned that very early," he said. "It really is amazing that some days you'll come out and you'll feel like you can beat anyone, and then some days you come out and you've got no confidence in the world and you can't break an egg with a hammer."

Woods has gone 18 months since his last victory, and he hasn't posted a top 10 since the end of 2013. He missed most of last year because of back surgery. He missed two months earlier this year trying to get his game up to his standards.

But after having to make key putts just to make the cut in his last two tournaments — and shooting a career-high 85 at the Memorial two weeks ago — it appears that Woods has taken more than a few steps back after his tie for 17th at the Masters.

Day said most fans know what Woods has done — 79 wins, 14 majors and No. 1 in the world longer than anyone — and that expectations remain high.

"We're just waiting for him to come back and win those tournaments like it was nothing," Day said. "But will we see it? I'm not sure. It just totally depends on the person, how hard he's working, because you don't get anywhere ... especially the top guys in the world, they're working their tails off.

"It's tough," Day added. "He dominated the game for so long, and that's what I admire about him the most. He dominated the game so long, and he was so motivated to win."

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RETURN OF JANZEN: Lee Janzen won his second U.S. Open in 1998 at The Olympic Club, but when his 10-year exemption expired at Torrey Pines, he never made it back. He narrowly missed qualifying one year. Two years ago, he was disqualified in a qualifier for wearing metal spikes at a club that didn't allow them.

And now that he's eligible for the Champions Tour, the 50-year-old Janzen is back in the U.S. Open. He earned his spot from a New York qualifier, and then he went up to Boston to play in a Champions Tour major. Next week, he has the U.S. Senior Open.

"I would say more than half the guys last week, they said, 'Hey, congratulations qualifying,' and then added a comment and it was usually like, 'What were you thinking?'" Janzen said. "Why do you want to go play all those flat bellies that hit it 350 yards on a course that you have to hit it 350 yards?"

Janzen said there will come a time when he no longer wants to play in his national championship. It's just not right now.

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HEALTHY DAY: Day is still waiting for the results to come back from one more sleep study, but for now, he's still lacking answers for why he suffered from severe dizziness that caused him to withdraw from the Byron Nelson less than a month ago.

"I feel good. I had three sleep studies done. I had a lot of blood tests done. I had an MRI on my head and my back -- my head and my neck. And everything came back negative," Day said on Monday. "So I have no idea what that was, other than I just may have been exhausted."

The dizziness was the latest in a string of health-related issues for the Australian, who started the 2015 season by winning at Torrey Pines. He's overcome back and thumb injuries in his past, only to be derailed recently by what he explained as just running "out of gas."

"I was training so hard, I was doing two-a-days every day coming into tournaments and then on top of it, I was doing practice, playing competitive golf and then trying to balance that with family, as well. It's just a full-time kind of gig there," Day said. "And I think I just ran out of gas and I wasn't feeling good, so I had the shakes and the tingling up my arms. And the loss of energy and strength was probably caused by that."

Day played the Memorial two weeks ago but missed the cut despite shooting 72 in the first two rounds. If his health wasn't a concern, Day would be considered one of the favorites this week at Chambers Bay, having finished in the top five in three of the last four U.S. Opens.

"I got off to a great start and was heading in the right direction. I hit a plateau, and I'm looking to change that this week," Day said. "I don't know what it is. Every time I get off to a decent start, there's something that happens. My thumb last year, and then whatever I had this year ... I'm glad it happened. I'm really glad it happened now, because then I can take action. I can understand what's wrong with me and then take action and move on, try and get better from it."

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DIVOTS: Six players were added to the field through the world ranking and the alternates. Kevin Kisner and Andy Sullivan were in the top 60. The four alternates were Kevin Chappell, Steve Marino, Jimmy Gunn and Josh Persons. Chappell now lives in the Seattle area during the summer. His wife grew up here and they recently had their first child, a boy named Wyatt. ... There were three generations of Texas Longhorns together on the range, even though they weren't far apart in age — 21-year-old Jordan Spieth (in his third year on tour), 20-year-old Beau Hossler (currently Longhorn) and 15-year-old Cole Hammer, who already has committed to Texas.

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AP Sports Writer Tim Booth contributed to this report.