Sivivatu completes a pacy back three alongside Roy Kinikinilau and Lelia Masaga.
Coach Ian Foster said: "Siti going to fullback is a small positional change for him.
"He is a class wing with two games under his belt. It is fair to say he has not been at the top of his game yet but he is a player with a lot of confidence.
"Along with Roy and Lelia in the back three and Siti at fullback, it will increase our attacking options."
Outside half Tasesa Lavea is replaced by Niva Ta'auso at inside centre, with the forwards unchanged.
The Highlanders are without captain Josh Blackie after the Junior All Black sustained a shoulder injury against the Cheetahs last weekend.
Former international Craig Newby takes the captaincy, while James Wilson steps in for full-back Glen Horton (ankle).
The Highlanders have also replaced their second five-eighth, with Aaron Bancroft losing the number 12 shirt to Callum Bruce.
Hoani MacDonald takes over from Kane Thompson at lock.
Three points divides the middle-of-the table Kiwis ahead of the derby, with a good run of form enough to push both teams into a play-off spot .