Sam Konstas has been confirmed for a Test debut after a stunning rise which started with back-to-back hundreds in the Sheffield Shield this season.
Konstas will be the fourth-youngest Test debutant and the youngest ever opener in Australia's history.
The 19-year-old will replace Nathan McSweeney at the top of the order after he lost his spot due to a lean run in the first three Tests.
McDonald praised the teenager for his composure since being named in the Boxing Day squad.
Sam Konstas of Australia speaks to the media. Getty
"He's been very similar to what I've seen on the outside … he's composed, relaxed, knows his game and is in a good place at the moment," McDonald said.
"He'll play Boxing Day, so I'll get that one out of the way.
"We said from the get go leading into the summer that we wouldn't shy away and age is no barrier.
"What he's shown is an array of shots and an ability to put pressure back on his opponents.
"… We're really excited for him, Boxing Day the biggest stage, you might as well get that one out of the way early."