Chiefs assistant coach Neil Barnes, who spent seven years as forwards coach with Canada, is impressed with what they bring to the group.
"Ross has impressed us since the first day we brought him in here to be honest and he has earned his stripes. You often have a person like that who just quietly goes about his business in the background and keep on improving," Barnes said.
"I know as a coach he is the type of player you tell him something once and the next time he turns out he has got that fixed up what you coached him. I have been really impressed. He is still a young man for a prop and he is making every post a winner at the moment. We have a lot of trust in him. He will do a good job for us."
Barnes also likes the cut of Thwaites, who he sees as "a bit of an old-school forward".
"To be honest they are right across New Zealand those type of guys. He was probably on the tools a couple of weeks ago. He has been working away doing his training earlier in the morning, getting a job done in the middle part of the day and still doing rugby at the other end of the day.
"So when he got the call-up he was in good nick. They're gold, those type of people, so I am sure he will make every post a winner when he gets his chance as well."
Tiaan Falcon keeps his place at first-five for the Chiefs with Damian McKenzie staying put at fullback. Veteran Liam Messam will start at No 8 as part of a dynamic loose forward trio with captain Sam Cane and Lachlan Boshier.
"We're very confident in Tiaan, he made a good fist considering he had only 10 minutes preparation for his first hit out. It's a bit of a confidence booster for him, so I'm sure he'll go well," Barnes said.
Chiefs team to play Bulls, Waikato Stadium, 7.35pm tonight.
1. Aidan Ross, 2. Nathan Harris, 3. Angus Ta'avao, 4. Brodie Retallick, 5. Mitchell Brown, 6. Lachlan Boshier, 7. Sam Cane, 8. Liam Messam, 9. Brad Weber, 10. Tiaan Falcon, 11. Solomon Alaimalo, 12. Johnny Fa'auli, 13. Anton Lienert-Brown, 14. Sean Wainui, 15. Damian McKenzie.
Replacements: 16 Liam Polwart, 17 Karl Tu'inukuafe, 18 Jeff Thwaites, 19 Michael Allardice, 20 Luke Jacobson, 21 Te Toiroa Tahuriorangi, 22 Marty McKenzie, 23 Declan O'Donnell.