The difference this time is the seat he'll be on the edge of is on the sideline rather than being in the stands.

There will be a strange sense of deja vu when the newest ACT Brumby searches for his family on Saturday night.

Three years ago he was sitting with them in the same stadium to watch the same two teams battle in what was older brother Ryan's debut.

Fast-forward to round four of the 2020 season and the Lonergans have packed their bags for another trip to Hamilton for a moment two Canberra juniors have been dreaming about since they were kids.

"I can't really remember the moment Ryan went on, but I've got a video of it. I know I got goosebumps, so I can't imagine how many goosebumps I have if I go on," Lachlan Lonergan said.

"I hadn't really thought about that, but if I get on at [the same ground], that will be pretty special. It's pretty weird, but cool as well.

"It's obviously a dream come true. We've talked about it growing up and said to mum and dad how cool it would be to play Super Rugby. To have that chance is pretty surreal, but exciting as well."

The Lonergans follow two sets of Smiths (George and Tyrone, and Ruan and Jean-Pierre) and a trio of Faingaas (Saia, Anthony and Colby) as Brumbies brothers.

Lachlan Lonergan has been added to the Brumbies' bench to help cover the loss of Folau Faingaa, who has been ruled out for at least one game with a toe injury.

Connal McInerney will be the starting hooker, with Lonergan to park himself next to Ryan on the reserves bench.

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The 20-year-old former junior Wallaby is being thrown into battle for what is one of the toughest challenges in the competition.

The Brumbies haven't won in New Zealand since 2014 and they haven't won in Hamilton since Lonergan was seven years old.

But the man coach Dan McKellar describes as a "tough little bugger" is unfazed by the task or the opposition.

"I feel like I put in a big effort in pre-season. I feel confident, and I've got two good hookers in front of me so they've given me good feedback," Lonergan said.

"I've been taking it all in. It's going to be tough, but I'll do my best.

"Deep down I still get nervous, but I more excited for the challenge and it should be fun."

Lonergan is the latest in a production line of Canberra talent to get their Brumbies opportunity. He joins Ryan Lonergan, McInerney, Joe Powell, Mack Hansen, Tom Ross and Tom Cusack as home-grown Super players.

"We call ourselves a family club, so I think it's a really nice moment for Ryan, Lachlan and the family. They've always been passionate Brumbies people," McKellar said.

"Both of the boys have come through our school system and pathways program, so it's nice for the family.

"Lachy is a tough little bugger. He's never going to be the biggest hooker, but we've seen what he can be capable of."

The Brumbies have blooded 12 Super Rugby rookies in the past two seasons, seven of those playing their first game in the first three weeks of this year.

The silver lining to that statistic is that none of them have bear the scars of a Kiwi losing streak over the past six years.

Some have never played in New Zealand, while only a select few of the game-day squad have tasted success across the Tasman.

Lonergan was one of the stars of the Australian under-20s campaign last year and the Brumbies rewarded him with a full-time contract and a leap into Super Rugby.

"I've put on three kilograms at the moment, Dan said to get a bit heavier and I still want to add a bit," Lonergan said.

"It was good playing overseas at a high level last year, but this weekend will be completely different."

The Brumbies have battled an outbreak mumps this week, forcing McKellar to change his team to chase a drought-breaking win.

Andy Muirhead starts on the wing and Toni Pulu joins the bench while Irae Simone makes his comeback from illness after he was diagnosed with the mumps last week.

"Some boys have acknowledged we haven't won [in New Zealand] in a while. But we can't change that, we can only dictate our future," Simone said.

"All we can do is go in with the mindset we're going to win. Personally the past doesn't faze me."

SUPER RUGBY ROUND FOUR

Saturday: Waikato Chiefs v ACT Brumbies at Hamilton, 5.05pm.

Brumbies: 1. James Slipper, 2. Connal McInerney, 3. Allan Alaalatoa, 4. Caderyn Neville, 5. Murray Douglas, 6. Rob Valetini, 7. Will Miller, 8. Pete Samu, 9. Joe Powell, 10. Noah Lolesio, 11. Andy Muirhead, 12. Irae Simone, 13. Tevita Kuridrani, 14. Solomone Kata, 15. Tom Banks. Reserves: 16. Lachlan Lonergan, 17. Scott Sio, 18. Tom Ross, 19. Nick Frost, 20. Lachlan McCaffrey, 21. Ryan Lonergan, 22. Bayley Kuenzle, 23. Toni Pulu.

Chiefs: 1. Aidan Ross, 2. Bradley Slater, 3. Atu Moli, 4. Michael Allardice, 5. Mitchell Brown, 6. Luke Jacobson, 7. Sam Cane (c), 8. Pita Gus Sowakula, 9. Te Toiroa Tahuriorangi, 10. Aaron Cruden, 11. Sam McNicol, 12. Alex Nankivell, 13. Anton Lienert-Brown, 14. Sean Wainui, 15. Damian McKenzie. Reserves: 16. Samisoni Taukei'aho, 17. Reuben O'Neill, 18. Ross Geldenhuys, 19. Naitoa Ah Kuoi, 20. Mitchell Karpik, 21. Lisati Milo-Harris, 22. Kaleb Trask, 23. Quinn Tupaea.