The Wallabies tighthead prop will trade rucks for dummies - not of the football variety - next week when he leaves Australia's Rugby Championship campaign for the birth of his child.

Alaalatoa will race home to Canberra following the Wallabies' clash with South Africa on the Gold Coast on Sunday night - a match which doubles as his 50^th Test cap - with wife Filo soon due to give birth.

So once he's done scrummaging against a monstrous South African pack featuring the likes of Steven Kitshoff, Bongi Mbonambi and Frans Malherbe up front, Alaalatoa flies home the morning after "for a whole different challenge".

"Probably not for me mate, I've got the easy job just being a soundboard or supporting my wife and the hard time she's going to go through," Alaalatoa smiled.

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"I'm looking forward to being there for her, obviously being away from home a couple of months, I haven't been able to be at home and support her there. Physically, it will be good to be home there and hopefully calm her down a little bit.

"Pretty nervous. It's awesome, I'm praying the rest of the journey goes well for my wife and I and our future bub. The wife is doing a solid at home, holding down the fort there.

"I haven't been home in a couple of months, so I'm looking forward to the opportunity and getting that balance in my life again. Being my best self also applies to what I do off the field and the man I am there. Praying the rest of the way goes well for us."

But first comes the matter of his 50^th cap for the Wallabies in a game they must win to keep their Rugby Championship ambitions above water.

The significance is not lost on a man whose father played Test football for Samoa.

"It's huge. Being born and raised in Australia, it was always a dream of mine to play for the Wallabies. Growing up in Sydney and being a part of the junior clubs, you're always watching the Wallabies when they play the Bledisloe Test matches or over on the spring tour as well," Alaalatoa said.

"It's always been a dream of mine to be a part of this squad. To represent this team and this country 50 times, man, it's a huge honour.

"When I take that opportunity this weekend I just want to deliver my best self, that's always the case for every game. I'm just grateful to be able to achieve that milestone on Sunday."

There may have been a temptation for Wallabies coach Dave Rennie to start the match with Taniela Tupou, but Alaalatoa's looming withdrawal at the midway point of the tournament was enough to suggest he could start the ACT Brumbies captain who will lay it all on the line.

"We're anticipating Allan leaving the squad after this Test, he'll head back to Canberra where his wife Filo is due to have a baby next week," Rennie said.

"That's probably the end of The Rugby Championship for him, so we'll get our pound of flesh out of Allan this week knowing we've got Nela and Pone Fa'amausili who should be back in time for the Argentinians."

Angus Bell earns a start at loosehead prop with James Slipper on the bench to counter the Springboks' six-two replacement split which "speaks volumes" about the way they want to play.

Slipper's ability to pack down on both sides of the scrum looms as a major weapon in Rennie's arsenal with three matches - one against South Africa and two against Argentina - still to come following Alaalatoa's departure.

"Slips has a different role this week. He's got a slightly different role this week but he has played a lot of footy," Rennie said.

"He could well give us a bit of tighthead cover when Al leaves, so we're keen to give him a run off the bench. Belly has been excellent, his ball-carrying gives us a point of difference."

THE RUGBY CHAMPIONSHIP

Sunday: New Zealand v Argentina at 5.05pm; South Africa v Australia at 8.05pm, Robina Stadium, Gold Coast.

Wallabies squad: 1. Angus Bell, 2. Folau Fainga'a, 3. Allan Alaalatoa, 4. Izack Rodda, 5. Matt Philip, 6. Lachlan Swinton, 7. Michael Hooper (c), 8. Rob Valetini, 9. Tate McDermott, 10. Quade Cooper, 11. Marika Koroibete, 12. Samu Kerevi, 13. Len Ikitau, 14. Andrew Kellaway, 15. Tom Banks. Replacements: 16. Feleti Kaitu'u, 17. James Slipper, 18. Taniela Tupou, 19. Rob Leota, 20. Pete Samu, 21. Nic White, 22. Reece Hodge, 23. Jordan Petaia.

Springboks squad: 1. Steven Kitshoff, 2. Bongi Mbonambi, 3. Frans Malherbe, 4. Eben Etzebeth, 5. Lood de Jager, 6. Siya Kolisi (c), 7. Franco Mostert, 8. Duane Vermeulen, 9. Faf de Klerk, 10. Handré Pollard, 11. Makazole Mapimpi, 12. Damian de Allende, 13. Lukhanyo Am, 14. Sbu Noksi, 15. Willie le Roux. Replacements: 16. Malcolm Marx, 17. Ox Nché, 18. Vincent Koch, 19. Marco van Staden, 20. Kwagga Smith, 21. Jasper Wiese, 22. Herschel Jantjies, 23. Damian Willemse.

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