Australian ace Jason Day has expressed sadness at Tiger Woods' plight but taken issue with the golf great's 'selfish' judgement for driving under the influence.

Woods has reportedly checked himself into rehab in Switzerland after being arrested and charged on March 27 after crashing his car near his home on Jupiter Island in Florida.

The five-time Masters champion's absence from the season's first major remains a hot talking point, with Day offering up his thoughts about his 'hero' after a practice round on Monday (Tuesday AEDT).

'It just shows the human element and the human side of someone that is struggling with some sort of an addiction,' the former world No.1 said at Augusta National.

'He's not immune to it just because he can hit a golf ball really well. He's had 25 to 30 something surgeries and, when you're going through that many procedures, it's painful coming out of those procedures.

'I've had procedures done and I typically try and stay away from all that stuff because I just know that ... painkillers, there can potentially be a downfall to it.

'Granted, when I look at that, I look at it and go, he's just a human being like everyone else and we have struggles.'

Day, though, said regardless of how invincible Woods may feel, he should never have gotten behind the wheel.

'It's unfortunate. The only thing that I don't understand is that it's a little bit selfish of him to drive and put other people in harm's way, as well,' the 2011 Masters runner-up said.

'But when you're the player that he was and how strong-willed he is, he thinks he can do almost anything, and that's probably why he's probably driving and a little bit under the influence.

'He was my hero - he is my hero. He was my hero growing up. The reason why I play golf is because of this tournament and Tiger. It's hard to see him go through what he's going through, and especially under the microscope.

'It must be hard to be who he is and have everything, everyone looking on, kind of down on him. Some people want him to fail. Some people obviously want him to succeed.

'It's really difficult for me to go through that and watch him, and I know that he's getting the help now, which is good. I'm just hoping he comes out on the other side and is better.'

Despite having undergone endless rounds of back surgery himself, Day said he could never know what Woods was feeling.

'It is tough. I've never dealt with an addiction before, other than golf,' Day said.

'I'm pretty addicted to that. But it must be tough to be isolated the way he is normally. He stays at home pretty much most of the time, doesn't really get out too much just because of how popular he is as a person.

'He's human and we all make mistakes. That's just part of learning and getting better, and I'm hoping that he gets the help that he needs and that he comes out stronger and better on the other side because, like golf misses him. We miss him here this week.

'It's always better when he's playing golf tournaments because we love having him around, so it's a little bit sad to not have him here this week.'

Woods' latest car crash and rehab stint has left Jack Nicklaus concerned over the golf icon's painkiller use, believing he is 'too far down the line'.

The golfing legend has announced that he is stepping away from the game to focus on his health and recovery after flipping his SUV.

Nicklaus didn't hold back as he expressed his alarm at Woods' condition, while insisting that he supported the embattled 15-time major winner, who is believed to have travelled to Zurich, Switzerland to check in to an ultra-private rehab facility.

Woods is also believed to have called President Donald Trump in the moments after his shocking car crash in Florida.