Ricky Ponting believes Australia's captain Steven Smith has the potential to finish his career as the greatest batsman of the modern era. Smith's century on the third day at the Gabba was the 21st of his Test career, in his 57th Test, and left him with a career batting average of 61.23.

Smith began as a legspinning allrounder but notably made a significant change to his game while batting in Perth during the 2013-14 Ashes, when he spontaneously added a preliminary movement to his technique. Since then, he has averaged 72.09 and scored 20 centuries. Ponting said his record put him on track to become the best batsman of the modern era.

"Twenty-one hundreds in 57 games, he's well and truly on track to do that," Ponting said on ABC radio on the fourth morning in Brisbane. "When you look at the way he went about it yesterday, he was just completely unflappable. He didn't get out of his bubble at all, through the course of that innings, which says a lot about him.

"I've watched him pretty closely, you can just tell he's hungry to lead his team well and he wants to be the best player that there has ever been. He's got a game now that is standing up to the best attacks in all conditions, all around the world. If he keeps trending the way he is, then absolutely."

"Think about the greats - the Tendulkars and the Kallises and these guys that have scored 15,000 and 13,000 runs, but they played in 150-plus Tests, Tendulkar 200 Tests, to achieve what they achieved. He's nearly halfway there in just over 50 Test matches."

Ponting added the caveat that things would not necessarily get any easier for Smith, noting that once a player gets near the 100-Test mark, it is difficult to keeping improving. Ponting was Australia's captain when Smith made his Test debut against Pakistan at Lord's in 2010, and he said that while nobody had expected him to become such a great batsman, it was always obvious that he had talent.

"I don't think any of us did, really," Ponting said. "He's clearly the number one ranked batsman in the world right now. We all knew he had talent, because he used to do things a bit differently. He would go to the nets and [you] throw him a pull shot, and he'd hit it straight back at you almost like a tennis shot. It's all different and unorthodox, but there's a certain amount of talent that goes with that."

Coming in the first Test of a home Ashes, Smith's Gabba century was not unlike Ponting's own Brisbane hundred in 2006-07, an innings that set the tone for Australia's whitewash of England. Ponting said Smith's effort this time around would have had a significant effect on some of the younger or recalled members of Australia's side.

"We saw the emotion that came out of him afterwards, banging his chest and his heart and his crest," he said. "But if I was sitting in that dressing room as a young bloke -- as a Bancroft or a Shaun Marsh coming back in, or Tim Paine -- I wouldn't have needed to see that at all.

"I would have been inspired by what I had seen in 520 minutes at the crease, and going up and down through the gears, and playing a role that was so specific to what the game needed. It was a leader's innings, and he's put his mark down on the series at the first possible opportunity."

However, Ponting said there was one thing about Smith's approach that he would like to see change.

"I still wish he'd bowl a few more leggies every now and then as well," Ponting said, "because he can bowl those and bowl those well."