Francis is expected to miss Friday's match against the Chiefs at Eden Park due to concussion after copping an errant swinging arm from Stormers second five-eighth Shaun Treeby on the chin in the 47th minute.
Speaking after the 30-22 loss which probably ends the Blues' playoff hopes, Umaga said the team doctor confirmed Francis was unconscious as a result of the blow. The first-five was taken from the field and replaced by Bryn Gatland.
Despite reviewing the incident and dishing out three other yellow cards, South African referee Jaco van Heerden and TMO Shaun Veldsman decided Treeby only deserved a penalty.
Asked whether it should have at least been a yellow card, Umaga said: "From what's happened in previous games you probably could say that. We made the right call bringing him off because he definitely was concussed. We now need to make sure he follows the right protocols in trying to get back and play when he can.
"We've got to deal with the decisions that are made on the field. That's what we talked about as a group.
"We knew going into this game the South African referees had been giving away a lot of yellow cards, and cards in general, so we talked a lot about being disciplined and we would expect that consistency throughout the whole game."
Treeby is now almost certain to be cited but that does not help the Blues' cause.
Umaga made it clear he would approach Bray for an explanation.
"I've got to go through the right channels in terms of reporting back - that's what we'll do to make sure we get some answers to some of the questions we have.
"There were some tough calls that we felt went against us but that's the way it goes. The Stormers brought a brutal intensity on defence and made it hard for us to build continuity in our game."
Blues wing Matt Duffie was sent from the field with 14 minutes remaining after being shown his second yellow card for diving on a player on the ground. Duffie's first card came early in the match for repeated team infringements after the Blues conceded four successive penalties near their line.
Earlier in the match the Blues scored two tries after Springboks lock Eben Etzebeth was binned for an open-handed push to the face of Akira Ioane.
The loss to the Stormers is likely to have quashed the Blues' playoff hopes, leaving them six points behind the Highlanders who play the Force in Perth on Saturday night.
While defeat in Cape Town provided the killer and controversial blow, and the unfair finals format does them no favours, the Blues will only have themselves to blame for missing the finals after five losses to Kiwi opposition.
"We always knew we had to win every game to be in contention. We obviously didn't do that tonight. It's disappointing but we've still got games to play and we want to make sure we finish on the right note. If we do get some results go our way you just never know.
"We've created a lot of opportunities to win games against Kiwi teams but we just haven't taken them. We've got to make good decisions when we get those chances because you don't get many."
Francis' absence for the Chiefs match is likely to see Gatland start at No 10, though Ihaia West and the uncapped Stephen Perofeta are in line to return from injury.
Photo: Gallo (Blues coach Tana Umaga was frustrated no card was given for incident which saw Piers Francis knocked out).