He made a dominant 109 not out for Big Bash League side Sydney Thunder after returning to fitness and forced selectors into a tough decision.
Shaun Marsh scored 182 in the first Test against the West Indies in Hobart but made way for Khawaja, who was treated for a stiff back late in his innings on Saturday but reported no trouble with his hamstrings.
Having scored three centuries in his past three Test matches, Khawaja is reaping the rewards of his hard work after suffering a huge blow in December of last year when he sustained a serious knee injury that sidelined him for several months.
"I wasn't in a very good place this time last year - I was just trying to stay positive," he said.
"I knew I wasn't going to play cricket for a while and wasn't expecting in my wildest dreams that I'd be playing for Australia again let alone playing in the Boxing Day Test.
"So I'm grateful every time I go out and play now."