Umaga said Faumuina had returned from the World Cup with a hamstring issue himself, although he was in outstanding form against the Chiefs last Friday.
The Blues coach said of Ranger, who is returning from neck surgery: "With Rene coming back from a long injury, he's still finding his feet a little bit and getting his game sense back so we thought it best he came off the bench. He's a pretty exciting person to come off the bench too.
"I have a philosophy that the bench have to come on and hopefully make things happen ... whether we're behind or in front. We need to keep the pressure on and the momentum going forward and if we haven't got momentum then they've got to shift it."
The Harley Davidsons will have to be finely tuned and working in unison on the highway if the Blues are to tip over their southern rivals, with Umaga suggesting the time for talking is nearly over.
He said: "The defending champions epitomise effort and worth ethic and a good culture and working for each other. That's what every team wants. We've talked a lot about it and we'll see how it goes."
The Blues team is:
Lolagi Visinia, Melani Nanai, Male Sa'u, George Moala, Tevita Li, Ihaia West, Bryn Hall, Steven Luatua, Blake Gibson, Joe Edwards, Josh Bekhuis, Patrick Tuipulotu, Sione Mafileo, James Parsons (c), Ofa Tu'ungafasi.
Reserves: Quentin MacDonald, Namatahi Waa, Charlie Faumuina, Akira Ioane, Kara Pryor, Billy Guyton, Matt McGahan, Rene Ranger.