If there is ever a shining role model for Cummins it is Harris, who has defied pain and logic to carve an astonishingly successful Test career after the age of 30, and wants to keep going for a while yet.

Cummins is still a month short of his 21st birthday and has played just two first-class games since his tantalising Test debut in Johannesburg in 2011. He returned from a back injury for the Perth Scorchers in the Big Bash League in January, and selectors have included him in a preliminary Australia A squad for a development series in the Top End this winter.

Harris will be assistant coach of the Australia A squad as he makes his own return from knee surgery, having bowled Australia to a famous series win over South Africa in Cape Town, but said his appointment should not be interpreted as a sign that the end of his international career is nigh.

"I'm not ready to hang 'em up yet," he said. "I've said the [2015] Ashes is a goal and I'll reassess after that. If I'm bowling well and we're winning games I'd like to think they'd still want me, but if we're not going as well and I'm not going as well, Darren [Lehmann] will tell me."

He is passionate about teaching the emerging quicks the principles that have underpinned the success of the Test attack. The A squad includes Josh Hazlewood, who had a breakout performance with 6-50 in the Sheffield Shield final, Mitchell Starc, Ben Cutting, Chadd Sayers, Jason Behrendorff and Cummins, who has been confined to short-form cricket in the short term.

"I'm probably looking forward to catching up with him [Cummins] the most," Harris said. "Just be patient. He's going to have another setback or two or three. It's how you deal with that. His body is nowhere near developed, it's going to take a couple more years, he knows he is good enough at international level, he's done it. It's just a matter of playing first-class cricket and getting strong.

''I can only talk from a personal perspective, but the more I play the better I get. You can't get conditioned for fast bowling unless you are bowling so he needs a good first-class season, maybe two, to get that right. Maybe he doesn't play all 10 [shield games for New South Wales], maybe he plays six or seven the first season, that's not up to me. But if you can get some good cricket under his belt other than four-over bursts it will be really good for him."

Harris was shattered to see Peter Siddle dropped for the Cape Town Test, a decision that has made him more aware than ever of the pressure exerted by the emerging quicks he will be mentoring.

Siddle, who is about to start a county stint with Nottinghamshire, was down on pace and replaced by James Pattinson for the deciding Test against the Proteas. The first change in the pace attack in eight Tests reinforced the fact there is little margin for form lapses.

"I was starting to doubt myself because I wasn't bowling well enough but I knew I could, and I bounced back in the last Test in Cape Town," said Harris, who is aiming to be fit for the Test series against Pakistan in the United Arab Emirates in October.

"With the amount of talent coming through, anyone can step up. With 'Sidds' going down, it was tough because Mitch [Johnson] and I had bowled with him the whole time and we had gone through a lot together. It was shattering to see 'Sidds' go, but he will fight back from that and it was an opportunity for James Pattinson who came in and did a really good job."

The selectors have loaded up on all-rounders for the series against South Africa A, India A and an Australian national performance squad, with James Faulkner, Moises Henriques and Mitch Marsh all included.

"The [selection panel] is especially keen for the potential future international all-rounders," national selector John Inverarity said.

The absence of Matthew Wade from the squad added intrigue to the question of which wicketkeeper is understudy to Brad Haddin, but Inverarity said Wade and Tim Paine were both "known quantities", and the A series would allow selectors a chance to look at rising glovemen Sam Whiteman and Peter Nevill.

"Matthew Wade and Tim Paine have had considerable international experience and are well-regarded, known quantities and the [selection panel] is hopeful that this international exposure with Australia A will provide Sam and Peter with invaluable experience."

NSW spinner Steve O'Keefe, who collected 41 wickets in the shield, and Queensland leggie Cameron Boyce were picked ahead of young Victorian James Muirhead.

The inclusion of Cameron White, the only Victorian in the 21-man squad, suggests he is back in the selectors' thoughts for the longer formats after an excellent season for the Bushrangers, while incumbent Test No.3 Alex Doolan will have a chance to consolidate after missing out on a Cricket Australia contract.

Australia A preliminary squad: Jason Behrendorff (WA), Cameron Boyce (Qld), Tom Cooper (SA), Pat Cummins (NSW), Ben Cutting (Qld), Alex Doolan (Tas), James Faulkner (Tas), Callum Ferguson (SA), Peter Forrest (Qld), Josh Hazlewood (NSW), Moises Henriques (NSW), Phillip Hughes (SA), Chris Lynn (Qld), Mitchell Marsh (WA), Peter Nevill (NSW), Steve O’Keefe (NSW), Kane Richardson (SA), Chadd Sayers (SA), Mitchell Starc (NSW), Cameron White (Vic), Sam Whiteman (WA).