Brumbies coach Stephen Larkham says commonsense will prevail and player welfare will be put first if the heat is too much to handle at the 6pm kick-off.

But Larkham wants his squad, which will be bolstered by the return of Wallabies Rory Arnold, Scott Fardy and Tevita Kuridrani, to embrace to brutal conditions to prepare for the regular season.

Mudgee is set to swelter with some forecasts predicting three days of almost 40-degree temperatures, including a high of 39 for the Brumbies-Waratahs trial.

Larkham and Waratahs coach Daryl Gibson have agreed to reformat the game into three 30-minute thirds to give them a chance to test combinations and player fitness.

But the heat will add another dimension to the match, with the Brumbies monitoring workloads and using ice towels in a bid to protect their players.

"We've had one trial in the heat now so our boys are somewhat conditioned, but it's only the second game of the season," Larkham said.

"We've got to be careful that we don't burn them out. We're very conscious of the time out in the sun ... we'll use common sense. If we need to have a water break, then there'll be a water break.

"We'll have a look at the forecast and make a decision on Friday night. We've been using ice towels ... but then the other side is that there are benefits of playing in the heat.

"There's a fine line and you don't want to push the boys over the edge in conditions like that, but we also want to get the most out of this game."

The Brumbies moved a training session to 6pm earlier this week to avoid Canberra's 39 degree temperatures but there was little respite from the heat.

"It's good for some guys, they'll lose a lot of weight," Fardy joked.

"It's just about managing [the heat] and staying hydrated. Even in a trial game, guys are pretty anxious and keen to get stuck in so there will probably be a lot of dropped ball anyway.

"It's just about getting game sharpness. Game fitness will come later."

Instead, the full squad has been pushed to its limits with Larkham calling on all of his fit players while the Waratahs will field a relatively unknown squad for their first trial.

The Brumbies will be without trio Scott Sio, Allan Alaalatoa and Jarrad Butler as they recover from injuries.

Wallabies props Sio and Alaalatoa have niggling hamstring problems while Butler has a lower-leg injury, but Larkham expects all to be ready for the opening round of Super Rugby.

"We're making sure we get them 100 per cent right before we put them out there," Larkham said.

"The pre-season has been relatively short for [Sio and Alaalatoa] and they've picked up some niggles over the last couple of weeks.

"There's no need to push them out for this game, we've still got the [Brisbane 10s next weekend] and then the star tof the season [on February 25.

"We feel those guys have enough experience to bring it out on game day for when the season starts."

SUPER RUGBY PRE-SEASON

Saturday: ACT Brumbies v NSW Waratahs at Mudgee, 6pm.

February 11-12: Brisbane Global 10s at Suncorp Stadium.

Brumbies team: 15. Aidan Toua, 14. Henry Speight, 13. Tevita Kuridrani, 12. Kyle Godwin, 11. James Dargaville, 10. Wharenui Hawera, 9. Tomas Cubelli, 8. Lolo Fakaosilea, 7. Chris Alcock, 6. Scott Fardy, 5. Sam Carter, 4. Rory Arnold, 3. Les Leuluaialii-Makin, 1. Nic Mayhew. Reserves: 16. Robbie Abel, 17. Faalelei Sione, 18. Ben Alexander, 19. Blake Enever, 20. Jordan Smiler, 21. Joe Powell, 22. Jordan Jackson-Hope, 23. Tom Banks, 2. Saia Faingaa, 4. Tom Staniforth, 7. Tom Cusack, 8. Ben Hyne, 10. Isaac Thompson, 11. Nigel Ah Wong, 13. Andrew Smith, 14. Andrew Muirhead, 6. Rob Valetini.

Waratahs team: 15. Bryce Hegarty, 14. Reece Robinson, 13. Irae Simone, 12. David Horwitz, 11. Harry Jones, 10. Mack Mason, 9. Jake Gordon, 8. Michael Wells, 7. Brad Wilkin, 6. Jack Dempsey, 5. Denio Toleafoa, 4. Ned Hanigan, 3. David Lolohea, 2. Hugh Roach, 1. Tom Robertson. Reserves: 16. Tolu Latu, 17. Damien Fitzpatrick. 18. Paddy Ryan, 19. Sam Needs, 20. David McDuling, 21. Matt Lucas, 22. Andrew Deegan, 23. Andrew Kellaway, 27. Ryan McCauley, 28. Jamason Schultz, 30. Con Foley, 31. Maclean Jones.