Fainga'a has lived a bench-warming existence since making his international debut in 2010, starting seven of his first 11 tests, before sitting behind Stephen Moore and Polota-Nau for 18 straight. And that doesn't include several more when left a frustrated unused reserve by Robbie Deans.
But Ewen McKenzie views Fainga'a's flexibility as a fast-striking scrummager under pressure as a key to Australia winning clean ball off their feed.
"We've been really impressed with the effort he has put in off the field recently, and he'll be determined to make the most of this opportunity," McKenzie said.
The set-piece is always an important area of focus for us, even more so when you play South Africa, and we know the outcome of the scrum and line-out will be crucial to the final result."
Not since 2006, when John Connolly experimented leading into the 2007 World Cup, has Australia resorted to five different starting hookers in a calendar year.
McKenzie has also recalled veteran prop Benn Robinson on the bench ahead of Pek Cowan because of his experience and loose-head nous.
"Benn is someone who we have always said wasn't out of the selection picture, and we've been pleased with the improvements he has made," the coach said.
Will Genia was overlooked for a bench spot with Nic White kept among three backs in a 5-3 split.
The Wallabies' hooker crisis in 2014
• Stephen Moore (knee reconstruction) - Lasted three minutes in year's first test in June.
• Tatafu Polota-Nau (knee and ankle) - Started twice before busting his knee, then lasted 40 minutes in return.
• Nathan Charles (shoulder surgery) - Ran on for both Bledisloe tests before another injury struck.
• James Hanson - No 4 in the pecking order has been left on the bench against the Springboks.
• Tolu Latu (broken arm) - Injured just days after joining the Wallabies camp last month.
• Saia Fainga'a - Sixth choice a month ago, now starting on the weekend in Cape Town.
- AAP