Usman Khawaja, who produced the finest knock of his test career at Adelaide Oval, insists he was unaware of being publicly put on notice by coach Darren Lehmann.

Lehmann made it clear to reporters after Australia's horrible loss in Hobart that only four players were guaranteed selection for the third test against South Africa: Steve Smith, David Warner, Mitchell Starc and Josh Hazlewood.

Whether it was a frank admission about selectors' dim view of the elegant left-hander or a ploy to motivate Khawaja, who is now the leading run-scorer of the three-test series, remains to be seen.

Regardless, it went over the head of the 29-year-old, who is rarely flustered on or off the pitch.


"I didn't know the coach said that. That's why I don't read the papers. I don't need to hear that," Khawaja said.

"People laugh at me but I genuinely don't read the papers."

Khawaja eventually fell for 145 early on day three of the day-night test.

He reached three figures on day two, resisting the Proteas' star-studded pace attack to build a first-innings lead of 124 runs for Australia.

The impressive knock started late on day one, when Khawaja was forced to open after a timely declaration from Faf du Plessis.

David Warner was off the field receiving treatment late in South Africa's innings.

"The boys are calling me nightwatchman at the moment, having a few jokes about it," Khawaja said as he prepared to bat for a third straight day.

"It happened all so quickly. When I saw Faf and Faf heard what was going on, I was like crap I'm going to be opening ... Faf declared the next ball."

Khawaja put a high price on his wicket, leaving the ball frequently as Australia crawled to 2-46 after 26 overs.

"I was about 12 off 70 balls and looking up at the scoreboard that's never nice. But I stayed out there long enough to score some runs which was pleasing," he said.