'One of my favourite Test moments': JL

Justin Langer can still remember the phone call that helped spark Usman Khawaja's stunning transformation in 2018.

Almost 25 years after his Test debut, Langer says Khawaja's diving catch to remove Indian skipper Virat Kohli on Thursday was "one of my favourite moments ever in my Test career", the culmination of months of physical exertion and coming after an emotionally trying week where the 31-year-old's mind has, at times, been understandably a long way from the Adelaide Oval.

Having shed 10 kilograms since the renowned fitness fanatic Langer was appointed coach in April, Khawaja's elevated athleticism helped him claim a catch on Thursday that could be a defining moment in the series.

"It was actually one of my favourite moments ever in my Test career, I reckon, for so many reasons," Langer told cricket.com.au in a Facebook Live before play on day two.

"It's the start of the Test series, it's Kohli, a great start for us, and with everything that's been going on with Uz.

"And also, the most important thing for me, I won't forget just after I was appointed (coach), I was sitting in the driveway in my house, talking to Uzzy about getting himself nice and fit so he could run hard between the wickets and field better.

"So when I see him take a catch like that, I was over the moon – for him and for the team."

Former Australian captain Ricky Ponting, who was an assistant coach alongside Langer on Australia's tour of the UK in June, offered an insight on Thursday into the "clear direction" the new coach gave his players when he took over the side.

"I know Justin's philosophies on that sort of stuff and it's fair enough," Ponting told cricket.com.au.

"These guys are highly paid professional athletes and when you have days like this (on Thursday) when it's 39 degrees, it's obviously going to be easier getting around when you're 10 kilos lighter."

But Langer was quick to point out that pledging to improve one's fitness is one thing, but being able to do it is another entirely.

"It just goes to show, that discipline," he said.

"We all talk about discipline, but for him to actually put it into practice … I'm so pleased for him, as he's a great role model now for a lot of players around Australia.

"And we're seeing it not only in his fielding but also in his batting. He's batting long periods of time, he's batting as well as ever. I'm really pleased for a lot of reasons."

Khawaja's catch was almost overtaken for fielding excellence on Thursday by a superb run out from Pat Cummins in the final session, the quick hitting the stumps from side on and while parallel to the ground despite having bowled 19 overs in energy sapping heat.

Mitchell Starc predicted on Thursday evening that his fast-bowling partner wouldn't be shy in regaling his teammates of his effort, and Langer confirmed the re-telling has started already.

"He might've sent it out on the team WhatsApp group last night, and he might have sent it to me last night, just reminding me how good he is," Langer said with a smile.

"But when you do something special like that, he can show off as much as he wants."

Domain Test Series v India

Dec 6-10: First Test, Adelaide Oval

Dec 14-18: Second Test, Perth Stadium

Dec 26-30: Third Test, MCG

Jan 3-7: Fourth Test, SCG

Australia squad: Tim Paine (c, wk), Josh Hazlewood (vc), Mitch Marsh (vc), Pat Cummins, Aaron Finch, Peter Handscomb, Marcus Harris, Travis Head, Usman Khawaja, Nathan Lyon, Shaun Marsh, Peter Siddle, Mitchell Starc, Chris Tremain

India squad: Virat Kohli (c), Murali Vijay, KL Rahul, Prithvi Shaw, Cheteshwar Pujara, Ajinkya Rahane, Hanuma Vihari, Rohit Sharma, Rishabh Pant (wk), Parthiv Patel (wk), Ravi Ashwin, Ravi Jadeja, Kuldeep Yadav, Mohammed Shami, Ishant Sharma, Umesh Yadav, Jasprit Bumrah, Bhuvneshwar Kumar