"He's going to give me to the nth degree to get there, but I'm praying for a miracle I think."
Hasler said Ennis was fighting an uphill battle to recover in time.
"Anybody knows that when you've got a fracture in your foot it's going to be a tough ask, so it's highly unlikely that he'll play," he told Triple M's The Grill Team.
Young playmaker Moses Mbye and reserve-grade hooker Damien Cook will both be considered to replace the 30-year-old Ennis, who also missed the 2006 grand final due to injury when playing for Brisbane.
NSW five-eighth Josh Reynolds could also be considered in the position in which he started his career.
But Ennis felt Reynolds was best kept in the No.6 jersey.
"If they went with Josh, I think they know that he's capable," the former NSW hooker said.
"But for me he's one of the best five-eighths in the comp and his combination with Trent Hodkinson is vital to our side there.
"It'll be interesting to see what Des comes up with."
Hasler gave no hint on Monday as to which way he was leaning.
"We'll just sit down and see what's the best fit," he said.
The Rabbitohs could also be without their star hooker Issac Luke for the showdown after he was charged with a grade-one lifting tackle on Sonny Bill Williams in Friday's preliminary final win over the Sydney Roosters.
Hasler said the NRL's match review committee "had to charge" Luke given the standard they've set this year in the wake of the devastating tackle on Newcastle's Alex McKinnon.
"And Souths, rightly so, will fight the charge," the coach added.
"They've got a good argument in there and no doubt they'll put a good argument forward."
- AAP