Jason Day has opted for rest over practice before defending his world No 1 status and his first major title when the 98th PGA Championship tees off Thursday at Baltusrol.

The 28-year-old Australian skipped practice on Tuesday over the par-70, 7 428-yard layout and opted for another rest day after spending Monday with his family, posting an Instagram photo from a video game centre.

Day, who hosted a champions dinner Tuesday night at the course, intends to play a full first practice round Wednesday at Baltusrol before playing the first two rounds alongside four-time major winner Rory McIlroy and five-time major champion Phil Mickelson.

American Dustin Johnson, who won his first major at last month's US Open, would overtake Day for the top ranking spot if he wins and the Aussie finishes worse than a two-way share of second – or if Johnson is a solo runner-up and Day is 29th or worse.

Fellow first-time major winners Danny Willett of England from the Masters and Sweden's Henrik Stenson from the British Open will play alongside Johnson on Thursday and Friday.

A field of 156 players, including 72 players from 24 nations outside of the United States, will compete for a $1.8 million (1.63 million euros) top prize from a $10 million purse.

Day will be playing his fourth event in five weeks and third in a row. But after withdrawing from the Rio Olympics over Zika virus concerns he will have a month off before the US PGA Tour's season-ending playoffs opener.

"It has been very difficult to plan my practice schedule around tournament schedule, because when I'm done, I take a few days off and I'm tired, and you've got to try and somehow manage that," Day said last week at the Canadian Open.

"The biggest thing is being able to prepare properly for the events, give yourself the best opportunity to win, and then try and do your best. That's all you can ask."

Two inches of rain fell Monday night at the course and more is in the forecast on Friday.

"The key this week is going to be on ball striking and staying patient because it's a pretty tough start, and then just kind of hanging on," Willett said. "Put it in the fairways and in the middle of the greens. Give yourself as many birdie chances as possible."

Long-hitters like their chances this week, especially with the only par-5 holes the 649-yard 17th and 554-yard 18th.

"If I can hit my driver halfway decent, I'll have a better advantage over some of the guys, at least half the field," said two-time Masters winner Bubba Watson.

"You have got to drive the ball well," said McIlroy. "It's a long golf course for a par 70 and the two par-5s coming at the end of the course. You've got to drive the ball in the fairway and pretty long as well.

"You're going to see a lot of guys hit a lot of greens. I think lag putting is going to be a big thing. If you have good speed on the greens, that's going to be a big help.

"Everything's is straight out in front of you. There's no real hidden secrets to it."

STENSON LIKES HIS CHANCES

McIlroy, Tiger Woods and Padraig Harrington have won the British Open and PGA crowns in the same year in the past decade. Before then it had been done only twice in 81 years. But Stenson likes his chances.

"If it behaves like it normally does, I think that can put me in good position," Stenson said. "It should play into my strengths, which is mid- to long-irons. So I think it's a good course for me."

And he opted to delay playing the back nine until Wednesday, saying, "I wanted to walk the course but I decided to conserve energy and not get out there any longer."

Mickelson, a 46-year-old US left-hander who won the 2005 PGA at Baltusrol, could become the fourth-oldest major champion in history by capturing the Wanamaker Trophy on Sunday after settling for second to Stenson at the British Open two weeks ago at Royal Troon.

"It will be important to drive the ball well, and I actually am looking forward to that challenge," he said.