The centre has been plagued by the injury since Round 5 of the NRLW season, and was cut from the extended bench on Saturday afternoon after failing a fitness test that would've seen her line up in her second decider.
The star is known as one of the competition's biggest hitters, though it's her leadership that's really dragged the Eels to the top of the heap, as did an honesty session with coach Dean Widders before Round 5.
The club appeared set to miss the finals before a final round win over Brisbane saw the blue-and-gold leap the Broncos into fourth, upsetting the undefeated Roosters in the opening week of the finals.
Abbi Church and Rikeya Horne once again shape as the club's centre pairing in Penitani's absence, named in the three and four jerseys respectively just a week after taking down the NRLW's greatest three-quarter pairing - Isabelle Kelly and Jessica Sergis.
While Penitani will miss the match, she might not leave the ground empty-handed, with replacement centre Abbi Church considering handing the captain her premiership ring if Parramatta can upset Newcastle.
“It's something that I've thought about and something that I've really considered because she's been there all season and she's earned that as our co-captain,” Church told The Sunday Telegraph.
“It's something I've been thinking about but I haven't told her yet, so let's keep it a secret.
“‘T' has been incredible.
“I said to her, ‘Please keep talking to me', because I wanted to learn as much as I could. I just asked her what she wanted from me and what the team needed out of that position.
“She's been unreal as a role model and a support for me. She told me to back myself, and hopefully I made her proud because she's as tough as they come.”
The two sides will both run out for their first NRLW Grand final appearance at 3:55pm on Sunday afternoon as the club's look to dust-off their trophy cabinet for the first time in decades.