Smith second only to Bradman after double ton

Australian captain Steve Smith has struck his highest Test score to become, statistically, the best batsman since Bradman.

Smith is unbeaten on 229 against England at stumps on Saturday's day three of the third Test in Perth to enter rare air.

DAY THREE: Unbeaten Smith, Marsh bat Aussies into big lead

SNEAKY JOE: Root's illegal act of Smith trickery exposed

'RUBBISH': Shane Warne lashes out at struggling Broad

'SOMEONE ELSE': England great makes shock captaincy call

His knock surpasses his previous Test-best of 215 against the English in 2015.

Only one batsman in Test history - the peerless Sir Donald Bradman - has a better average than Smith.

With his second Test double century, Smith's average has risen above 62 - well shy of Bradman's 99.94, but the next best in Test cricket.

And only two batsmen - Bradman and West Indian legend George Headley - have a higher percentage of centuries per Test innings.

Bradman scored a ton in 36.25 per cent of his innings followed by Headley (25 per cent) and Smith (20.37 per cent).

Smith's sheer brilliance, and unorthodox technique, has been compared to Bradman by Test great Adam Gilchrist.

Gilchrist reckons Smith's unusual technique should prompt coaching manuals to be torn up.

"It's everything you don't teach," Gilchrist said of Smith's style while commentating for BT Sport.

"But he has got Bradman-like numbers so why don't we encourage it?

"There's a lot of Sir Donald Bradman about the backlift and down swing.

"You are watching a master craftsman at work."

Ex-Australian captain Ricky Ponting said Smith "does things at a different level" to other batsmen.

"His basics just look slightly different than everyone else," Ponting said on BT Sport.

"He plays the ball on its merit and it hits the middle of the bat."

Former England batsman Kevin Pietersen, flanking Ponting in the commentary box, said Smith's eagle eye was astonishing.

"The speed with which he picks up the ball from the bowler's hand is something to be admired," Pietersen said.

"The great players can pick gaps and he's picking gaps ... he does the basics right and he's sticking to his way."