But he said he knew his best was no longer good enough.

That realisation was why  Australia's best batsman since Bradman decided to draw the curtain on his illustrious international career.

The Mowbray batsman will today enter a Test arena for the 168th and last time on the same ground that he began his Test journey in 1995.

``It was a decision I thought long and hard about,'' Ponting said yesterday in an emotional press conference in Perth.

``At the end of the day it was based on my results in the series so far.''

Ponting has scored just 20 runs in his past three innings against the South Africans. 

``It's not what I expect of myself and it certainly hasn't been to  up to the level required of batsmen and players in the Australian team. 

``As I've said all along, I continue to play this game as long as I feel I can contribute to wins and play well enough to help teams win games, but over the last couple of weeks my level of performance hasn't been good enough to do that.''

Ponting, who will turn 38 next month, made it clear that he did not receive the dreaded tap on the shoulder from chairman of selectors John Inverarity.

He said thoughts of retirement had only entered his head in the past week.

``It was towards the end of (last week's) Adelaide game that I started to contemplate what it might mean,'' he said.

``I started to contemplate within myself whether I was good enough to play the way I have during the years and the thing that struck home most with me, was that only a few weeks ago I thought my preparation was as good as it had been in a while.''

An emotional Ponting delivered the news to his teammates yesterday morning.

The man who took over from him as skipper, Michael Clarke, was in tears at a press conference that followed the Tasmanian's announcement.

Ponting deflected talk of making yesterday a look back on his career.

He said that was because he still had something to achieve against South Africa.

He was confident he could ``contribute to a great team performance and do what I can to get a win for our team, and if we can get back to top of the tree and number one in the world''.

Ponting enters his final Test as Australia's greatest run-scorer with 13,366 runs from 167 Tests at 52.21.

He scored 13,704 one-day international runs at 42.03 and 401 Twenty20 international runs at 28.64.

He will join Steve Waugh as Australia's most capped Test player. He would have taken that record if his career had extended to Hobart's Test against Sri Lanka next month.

Ponting went into this series looking in great touch after strong early-season form for Tasmania, where he averaged 118.33 in the Sheffield Shield.

But he was unable to replicate that against the South Africans, with his poor showing against the world number one's pace attack signalling the end.

Ponting will play out the summer with Tasmania in the Sheffield Shield and one-day competition, as well as with the Hobart Hurricanes in the Big Bash League.