Chairman of the National Selection Panel Rod Marsh has resigned from his position effective immediately in the wake of Australia's disastrous start to the Test summer.

At this stage, no replacement for Marsh has been named, with the Cricket Australia Board set to hold an extraordinary meeting later this evening, where a decision on an interim appointment is expected to be reached.

With Australian cricket in turmoil after the Test team lost the opening two matches of the series to South Africa – the second by an innings after a calamitous pair of collapses across three days of play in Hobart – Cricket Australia CEO James Sutherland earlier today forecasted changes ahead of next week's day-night Test in Adelaide.

However, those changes had referred to playing personnel, and in speaking on his decision to end his two-and-a-half year tenure in the position, Marsh said he had not been forced out of the role.

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"This is my own decision and no-one within Cricket Australia has pressured me or even suggested that I should do this," the 96-Test veteran said.

"Clearly, though, it is time for some fresh thinking, just as it is for our Test team to welcome some new faces as we build for the future.

"I have always had the best interests of Australian cricket foremost in my heart, and that's why I have made this decision.

"I wish the captain, coach and the team all the best going forward. We will be great again."

Last month, Marsh signaled he would leave his post when his contract was due to run out in June next year but has now decided to end his tenure early.

Marsh, in conjunction with his fellow selectors Darren Lehmann, Mark Waugh and Trevor Hohns, oversaw three changes to the Australia side that was beaten in Perth in the first Test.

Joe Burns replaced an injured Shaun Marsh, and South Australian pair Callum Ferguson and Joe Mennie both made their Test debuts in place of Mitchell Marsh and Peter Siddle (also injured).

Following the second Test defeat however, coach Lehmann indicated more changes would occur ahead of the third Test, beginning November 24 in Adelaide, with the upcoming round of the Sheffield Shield, beginning tomorrow, pivotal in that decision-making process.

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“There'll definitely be change,” Lehmann said. “The guys have got to play Shield cricket. By the end of the Shield game we'll have a squad for you.

“I thought (Josh) Hazlewood was great, (Mithcell) Starc's getting back to his best and then you've got (Steve) Smith and (David) Warner.

“Outside of that everyone's got to make some runs and take some wickets.

“It's a really important four days of Shield cricket.

“The lads are really keen to get out of here and get ready to play that game and prepare the best they can.

“(Existing) spots, performances are going to count, but you've got to have an eye to the future as well, it's trying that juggling act.”

What impact – if any – the resignation of Marsh will have on that outlook is unknown, however the run of five Test defeats on the trot appears to have forced the selectors' hands.

Cricket Australia’s Chairman, David Peever, thanked Marsh for his tenure and involvement in Australian cricket.

“Rod has played a pivotal role during a time of change in Australian cricket, which has seen the team hold the top positions in both Test and One-Day rankings as well as secure an ICC Cricket World Cup victory," Peever said.

“We understand this decision has not come easily for Rod and on behalf of Australian cricket we thank him for his leadership and the integrity and insight he brought to the role throughout his tenure as the National Selector and the lifelong commitment he has given to our sport. Above all else, Rod is an outstanding person.”