Messam will captain the side from blindside with impressive debutant Johan Bardoul dropping out of the match day 23. Cruden comes in at first-five to replace Damian McKenzie, who shifts to the bench.
With Tim Nanai-Williams and Tom Marshall ruled out through injury and Gear picked to start on the left wing, James Lowe moves to fullback while Bryce Heem, who was another late replacement against the Blues, retains his spot on the right wing.
Hooker Quentin MacDonald and Taranaki centre Seta Tamanivalu are the new faces in the reserves.
Chiefs to play the Brumbies:
1. Jamie Mackintosh, 2. Hika Elliot, 3. Siate Tokolahi, 4. Matt Symons, 5. Michael Fitzgerald, 6. Liam Messam (c), 7. Sam Cane, 8. Maama Vaipulu, 9. Brad Weber, 10. Aaron Cruden, 11. Hosea Gear, 12. Sonny Bill Williams, 13. Charlie Ngatai, 14. Bryce Heem, 15. James Lowe.
Reserves: 16. Quentin MacDonald, 17. Pauliasi Manu, 18. Ben Tameifuna, 19. Brodie Retallick, 20. Tevita Koloamatangi, 21. Augustine Pulu, 22. Damian McKenzie, 23. Seta Tamanivalu.