As a former teenage debutant, Australian captain Pat Cummins has a better concept than most about the experience new Test opener Sam Konstas has enjoyed this week ahead of Boxing Day Test.

The 19-year-old Konstas will become Australia's youngest Test debutant since Cummins took the field against South Africa at Johannesburg in 2011.

After taking 6-78 as an 18-year-old at the Wanderers against South Africa, Cummins said he approached his debut with the approach that he had nothing to lose at the time.

"I think you always want to do well (but) I was saying this to Sam the other day, I remember that as an 18-year-old, I was thinking I got a lot more leeway because I was young," Cummins said on Christmas Day. 

 "It almost felt like if I didn't have a great game, it wasn't my fault. It was the selectors' fault for picking me. I was like, 'Well, they're the idiots who picked an 18-year-old.'

"You're so young starting out your career (and) it's Boxing Day. It doesn't get any better than this, so just enjoy the moment."

"There's a level of naivety that you just want to go out and play, like you do when you were a kid in the back yard, you just want to take the game on and have fun and not overthink it.

"That's the message to Sam."

As expected, there will be only two changes to the Australian team, with Konstas replacing the dropped Nathan McSweeney and Scott Boland replacing the injured Josh Hazlewood.