Hanson and Davies both had to be substituted at half time during Wednesday's win at Leyton Orient due to tight hamstrings.
Although he was able to carry on until the finish, Morais is ruled out as well after jarring his knee while tackling Orient's Marvin Bartley in the first half.
To add to Parkinson's troubles ahead of the Walsall game, Jon Stead remains a big doubt for this Saturday due to the same ankle wound that kept him out of the midweek win at Orient.
As a result of the added injuries in the camp, Parkinson knows City will now need a big effort on and off the pitch come kick off.
Parkinson said: "Everyone is going to be needed now after the disruption we've had.
"The injuries we have picked up over the last four or five days have hit us hard.
"We will need the crowd more than ever come Saturday afternoon. It is going to be one of those days where the crowd can make a real difference no matter who is out there on the pitch for us.
"The lads have been fantastic in the last week or so and it is going to need another huge effort from everybody at the weekend.
"Filipe and Jon Stead are more impact injuries which you can't do too much about. You simply have to let them settle down. James Meredith also has a slight issue as well.
"We don't think Dava's (Andrew Davies) injury is too bad either.
"Hanson's (injury) does look at bit more significant unfortunately. Hopefully it could just be a bit of fatigue but the early signs indicate that the injury is worse than Dava's."
Due to the recent injuries to Stead and Hanson, Parkinson has also confirmed that he will be recalling Oliver McBurnie from his loan spell at Vanarama Conference side Chester FC.