The Sharks received a massive personnel boost on Monday, with Braydon Trindall training and Fonua-Blake revealing he expected the star five-eighth to play.
But Cronulla players were also left to admit their disappointment at not being allowed to face North Queensland at Shark Park, with the game instead set for Allianz Stadium.
The NRL's decision comes after years of debate around finals venues, with Shark Park the most scrutinised given its currently-reduced capacity of 13,500 amid an ongoing leagues' club reconstruction.
Cronulla bosses had been hopeful the fact the club were playing the Cowboys would allow the game to be played at a suburban ground, given the likelihood of fewer away fans.
But that hope was officially snuffed on Sunday, raising questions over whether Shark Park would ever host a finals match again.
"It's not ideal," Fonua-Blake said.
"You work so hard during the year to get a home semi and for it to be taken away, it's unfair.
"It's the incentive for finishing higher on the ladder, and to not get it, it's a bit unfair."
The NSW State of Origin prop said his concern was driven by the fact most clubs could play at their home stadium.
"To play in front of your home crowd, it feels like you have a 14th player on the field sometimes," he said.
"It's a bit unfair, but what can you do? The call has been made above our heads.
"We've just got to cop it and get ready to go out and put in a good performance this weekend."
The NRL changed its rules at the end of last season to give it the ultimate say on where finals would be played.
But Australian Rugby League Commission chairman V'landys insisted on Monday that the door was not forever shut on all suburban grounds hosting finals in the future.
"We're going to look at every game on its merits," said V'landys, who is also currently acting as NRL executive chairman.
"We still want to try to keep the suburban grounds as much as possible.
"But when their capacity and their facilities aren't there at the standard you want, you've got to shift them.
"Unfortunately, at the moment, Shark Park, I don't think anyone can argue, isn't that facility where you're giving the fan the ultimate experience."
When asked how Cronulla took the news, V'landys said it had been made with the club's fans in mind.
"A lot of Sharks fans wanted to go to Allianz, believe it or not," he said.
"And we wanted to accommodate them. Plus, we wanted to accommodate a lot more fans.
"Why would you have a billion-dollar venue sitting there doing nothing? Why not give fans the ultimate comfort and the ultimate experience?"
