Australia's fallen star needed a sponsor's invite into the prestigious 78-man CJ Cup in Las Vegas starting on Thursday and will use the no-cut event to gauge where his game is at, having not played in almost two months.

The former World No.1 has slumped to 79th in the rankings and needs to return to the top-50 – or win a tournament – to qualify for The Masters, U.S. Open and The Open in 2022.

Once a perennial contender at the majors, Day is so far only exempt for the PGA Championship next May as a former champion.

"I'm a different player than what I was five years ago. I'm a different person. I have different priorities," said Day, who is also juggling a hectic family life after welcoming the birth of his fourth child this year.

RIGHT: Day last won on the PGA Tour in 2018 at the Wells Fargo Championship. PHOTO: Streeter Lecka/Getty Images.

"I can't work as hard as I used to just because of my body, and I'm OK with that."

The 33-year-old knows he must work smarter, not harder to be able to compete with his chronic back injury.

"I'm not trying to do the exact same thing that got me to No.1 in the world," Day said.

"I know that if I did that, I wouldn't get there because my body wouldn't handle it.

"So I've got to somehow be able to kind of learn as I go along and try and adapt as best I can."

Day's physical impediments have also taken a big toll on the Queenslander emotionally.

"We all battle demons, especially as golfers. It's such an individual sport," he said.

"(I) just (want to) try and discover that golf is not the thing that defines me."

Without a win since 2018, Day hopes working on his body and mind will extend his career for a decade or more.

But he knows he's at a crossroad.

"Trying to work on myself personally, which is something that we don't do enough of as professional athletes. And then on top of it, trying to work on my swing to help complement the mind and body.” - Jason Day.

"You learn to go ... I'm either going to quit the game because I don't want to feel like this and it's not motivating and I'm struggling with it, or how do I handle it and tackle it head on and be able do it in a healthy way where for the next 10, 15 years, if I want to, I actually enjoy myself on the golf course while competing at a high level," Day said.

"Do I want to climb that mountain again?

"For sure. But I've got to take it easy and I've got to be smart about it because, if I'm not smart about it, then it could be short lived."

Day also admitted his return to the Tour will be short lived, lasting only this week before likely making his next start early next year at the Farmers Insurance Open at Torrey Pines.

“I mean, I played – from the British Open, played the FedEx, then I'm playing this week and I'm scheduled to play the Shootout, and then the next tournament I'll play is Farmers. So I guess that's three, three events in five, six months, something like that,” he said.

“Focusing a lot on my mind, focusing a lot on my body. Both are very much important, like both body and mind. Trying to work on myself personally, which is something that we don't do enough of as professional athletes. And then on top of it, trying to work on my swing to help complement the mind and body.”

Australian No.1 Cameron Smith will also tee it up for the first time this season, while Marc Leishman, Adam Scott, Matt Jones and Cam Davis are backing up from last week as 36 of the world's top-50 players feature at The Summit Club.

- Additional reporting by Jimmy Emanuel.