Masaga, who was a try-scorer in the Chiefs' 20-19 semifinal win over the Crusaders, has an ankle injury and has been bracketed on the right wing with Robbie Robinson.
Coach Dave Rennie has maintained the midfield pairing of Andrew Horrell and Charlie Ngatai and chosen prop Ben Tameifuna to start ahead of Ben Afeaki.
Masaga, captain Craig Clarke and prop Toby Smith will all play their last matches for the Hamilton-based Chiefs before taking up contracts in Europe.
Rennie said "we want to send these outstanding Chiefs men out on a high with back to back titles."
Teams:
Chiefs: 15 Gareth Anscombe, 14 Lelia Masaga or Robbie Robinson, 13 Charlie Ngatai, 12 Andrew Horrell, 11 Asaeli Tikoirotuma, 10 Aaron Cruden, 9 Tawera Kerr-Barlow, 8 Matt Vant Leven, 7 Tanerau Latimer, 6 Liam Messam, 5 Brodie Retallick, 4 Craig Clarke (captain), 3 Ben Tameifuna, 2 Hika Elliot, 1 Toby Smith.
Substitutes: 16 Rhys Marshall, 17 Ben Afeaki, 18 Michael Fitzgerald, 19 Sam Cane, 20 Augustine Pulu, 21 Bundee Aki, 22 Robbie Robinson or Patrick Osborne.
Brumbies:
TBA