Watson will be meeting with an independent neurologist on Thursday in a last-ditch bid to be approved to take the field for one final time as a Rooster, after suffering a concussion in the preliminary final win against the Dolphins.
The NRL's protocol requires any player diagnosed with a category-one concussion, like Watson was, to be automatically sidelined for 11 days.
The initial ruling was upgraded to a category one after it was originally treated as a less severe category two, which does not require the mandatory stand down period. The Roosters are appealing that change.
Standing ready to replace him is Ioelu, the Roosters academy graduate who made his NRL debut last year and has 17 first grade games to his name.
"It's hard to put it into words, you always play the image in your mind as a little kid," Ioelu told AAP.
"Being here this week and this moment, you're just super grateful for the opportunity that you've been given."
Ioelu moved from Auckland to the Tricolours as a teenager, where he became academy housing flatmates with Robert Toia, Salesi Foketi and Siua Wong - who have broken into starting first grade roles over the last couple of seasons.
For Ioelu, he is trying to remain level-headed even with the prospect of becoming the starting hooker for Sunday's decider.
"Your mind can play a lot of tricks on you, thinking that your role is bigger than what it is," the 22-year-old said.
"But just knowing that your role is still the same, you don't need to change much, you don't have to do much if you're playing with Teddy (James Tedesco), Rads (Victor Radley), Mark (Mark Nawaqanitawase), Toups (Daniel Tupou), let them do their work and your opportunities will come."
