Three months on, the Australian skipper is at his lowest point with his reputation irreparably tarnished by a ball-tampering scandal that threatens to end his captaincy.

Smith has confessed he and the leadership group hatched a scheme for Cameron Bancroft to use tape to illegally interfere with the ball on day three of the third Test against South Africa in Cape Town.

In an extraordinary press conference at the end of the day's play, Smith said he was "embarrassed" and admitted his integrity deserved to be called into question.

Asked whether he would consider stepping down as captain, Smith was adamant he remained the best person for the job.

That decision may well be taken out of his hands with Cricket Australia chief James Sutherland on Sunday declining to guarantee Smith would retain his position.

To stand down in disgrace would be a remarkable turn of events for a mild-mannered captain with a reputation as a cricket nerd; a batsman better known for his quirky habits at the crease than his off-field exploits.

Smith's autobiography, released in the lead-up to the Ashes, devotes pages upon pages to discussing his batting technique and only briefly touches upon his life outside of cricket.

The world's No.1-ranked Test batsman took his game to another level during Australia's 4-0 Ashes triumph, averaging a Bradman-esque 137.4 and earning man-of-the-series honours.

Such accolades now appear certain to be overshadowed by the moment in Cape Town when Smith's fierce competitive instincts led him to make an appalling error of judgment.

Should Smith's captaincy come to an end, finding a suitable replacement looms as a major headache for CA.

It is not yet clear exactly who was involved in the Cape Town saga but vice-captain David Warner, Mitchell Starc, Josh Hazlewood and Nathan Lyon have all previously served in the leadership group.

"If something is to happen to Steve Smith, then the captaincy cannot go to anybody that has been involved in this situation," former Australian skipper Michael Clarke said on the Nine Network.

Mitch Marsh has long been viewed as a future captain but, like Tim Paine, has only just returned to the side, while Shaun Marsh and Usman Khawaja's form remain a concern.

The highly-rated Pat Cummins looms as a smokey, although fast bowlers have rarely been called upon to assume Test captaincy duties.

Australian Associated Press